I have tried:

• Wearing a vibrating compass anklet for a week. It improved my navigational skills tremendously. I have low income, but I would definitely buy one if I could afford it.

• Listening to a 60 bpm metronome on a Bluetooth earpiece for a week (excluding showers). I got used to the sound relatively quickly, but I most definitely did not acquire an absolute sense of time. However, I noticed that during boring activities such as filling out paperwork, the ticking itself seems to slow down.

I will try:

• Wearing an Oculus Rift that shows the Fourier Transform of what I would normally see. I'd like to know if I can get used to it, and if it improves my mathematical intuition.

Upgraded reflective senses would be really cool. For instance:

• Levels of various interesting hormones like cortisol, epinephrine, testosterone, etc. For instance, cortisol levels are higher in the morning than in the evening, but this is not obvious. (Or am I lying to prevent hindsight bias?)
• Various things measured by an implanted EEG. For instance, it would be cool to intuitively know the difference between beta and gamma waves.
• Metabolism-related things like blood insulin, glucose, ketones.
• Galvanic skin response. Heart rate variability.

We already have weak senses for most of these, but they're not always salient. Having a constant sense of them would allow you to do biofeedback-like training all the time.

• Ionizing Radiation - preferably expressed as synthetic heat or pain with a tolerable cap. The various types could be differentiated, by location or flavor, but mostly it's the warning that matters.

Being able to "feel" electric/magnetic fields with your hands would be great. Not dissimilar to wifi sensing, but enough to be able to intuit what a circuit is doing just by observing/feeling it.

I also don't think that anyone's mentioned having a true internal clock. Some people can already wake up at a specific time of day just by wanting to - that'd be useful. Also for the ability to time things.

Lastly, while being able to detect neurotransmitter levels in your own brain would be great, being able to detect them in the brains of others would be even better. Kind of a toned-down empathic ability - you could tell who was stressed, who was happy, and so on by the amount of cortisol or dopamine in their brain.

Similar to true north, a sense that always points to a specific person. I think this might non-obvious use for people with poor attachment who can lose, on a deep level, a sense of being connected with someone when they're not physically around, and can need a while to build it up again when that person comes back. Also for young kids, who sometimes experience the sensation of not knowing where their mom is as quite traumatic.

Could be fun to be able to see relations between people and tweak which ones show up as different false color lines between them on the fly.

Facebook friends Past/Current romantic relationship Went to school together Coworkers

Though I expect people to find this creepy despite the fact that most such data is publicly available.

Reliable internal senses: in effect, a diagnostic readout of chemical and biological processes, such as blood glucose, melatonin and other hormones, immune responses, calories consumed, hydration, organ function, and so on.

This doesn't have to be a sense as such (that is, directly available to consciousness). It could be a collection of timeseries sent to an external monitoring system.

How about: as a commitment mechanism, a small but nagging amount of discomfort related to your procrastination on a measurable task. I'm picturing this working something like the need to pee, with the difference that it resets at night: the discomfort could build throughout the day and instantly be resolved when you completed the task and reduced as you work toward the task.

For instance, if you committed to exercising a certain amount, accelerameters could estimate physical activity. for every step you took, your discomfort would decrease and for ever hour you sat on the couch, your discomfort would grow.

Possible commitments this would work with: exercise anki decks habbitrpg points spend a certain amount of time talking per day (for the recluse/introvert trying to train social skills)

Another example of this is vOICe. It converts images directly into audio, and people can quickly learn to see with it.

Also Neurofeedback, where you see your own brainwaves and then try to control them. The theory being that you can learn to make your brain focus or relax.

A 'taste' for pathogen bacteriae in food.

• High-speed direct information/language port (combined with a camera/text recognition software, or phone with wifi). Eyes are not optimized for reading at the maximum speed the brain can handle, and as http://www.spritzinc.com/ shows even fairly basic hacks can give huge gains. I bet we could push it much further. Especially good for the blind.
• Glasses which convert various interesting non-visible wavelengths of light into a specific one (possibly camera+projecting onto google glass, possibly using the hearing thing?), gradually cycling through different wavelengths in a predictable way. There's a lot of detail we miss out on by only sensing three colors.
• Whiskers for air current sensing. Probably needs a wide channel though.
• Not exactly a new sense, but total area awareness via a swarm of microdrones with cameras/microphones (and split projection onto glasses) would be pretty awesome. Like a poor man's Skitter.

For diabetics, a blood sugar monitor.

Bottlenose can be built at home and gives a very primitive sense of echolocation.

Echolocation was the first thing that came to mind for me. Do you have more info about this? I couldn't find anything on google.

I often wished for a little drone, equipped with a camera, some other recording software, and wings to do the legwork for me. Imagine sitting on the edge of a swamp, in your car, with a monitor built in your glasses showing you what the drone sees,and ssending it where you want it by moving your fingers. Of course, it can be done without implanting anything in one's head, but generally, people want to carry as little as possible... It would open new eras in waterfowl population research, too.

ETA: thank you all for your answers!

perfect north

There are quite a few hacker projects and at least one serious research project for a compass sense e.g.

• north paw

• feelspace belt

See also sensory augmentation

Emotion detector/encoder/transmitter/decoder/injector would be quite useful to the less neurotypical of us. The emotion injection part seems the hardest.

Interesting that all your proposals look outward. I primarily would want to monitor my own body. I want to detect cell growths of the type that could become cancerous and so on. Essentially improve on the sense of pain, give a "warning buzz" way before a problem grows big enough to affect the pain nerves.

Who should I talk to in a group? I have a bunch of existing "social senses" for navigating this, but they're not very reliable. If a clear You-Should-Talk-To-This-Person sense went off whenever I encountered someone appropriate, that would be nice.

• compress global twitter sentiments into 24 channels. Will you begin to have an intuitive sense of global events?
• encode stockmarket data. Will you become an intuitive super-investor?
• encode local weather data (a much more advanced version of "I can feel it's going to rain in my bad knee)

Only if you have a chance for immediate feedback. And I don't see that for any of these three as you can neither influence them directly nor filter to observe relevant parts. The latter might show a way to make this useful.

compress local (on the topics of the website you are browsing) twitter sentiments into 24 channels. Will you begin to have an intuitive sense of the character of the site?

a few of your suggestions can be summarised to "other electromagnetic senses" (being things of other wavelength than visible light), and generally things not in the "sound range" either.

Magnetic sense has been mentioned several times; I am going to look at getting a magnetic ring; never thought of it; and would be keen to try it. (and the non-invasiveness sounds good to me)

Someone mentioned already - internal vs external senses. I would like the ability to sense my own body temperature (possibly at my extremities vs my core, although I don't think it is known whether these details related to productivity - I would also like to know that), a general feel for my heart rate (this is coming along with wearables, but slow).

in order to sense electromagnetic radiation there needs to usually be a controlled source that you detect. So some kind of emission source of a particular wavelength that you can feel changing. (in the same way that we see different colours because light waves bounce off things differently)

I would like to have a sense of "density" of objects, I often find myself tapping on things to "check" but not really being able to describe why I do that. In addition to this a vibration sense - for the low-audio-wave frequencies of .01-50hz (you can hear them but I would like to feel them and take better note of the patterns they produce)

Perhaps a "purity sense" to be able to determine if a thing was a pure substance or one with imperfections (either a metal or a diamond etc) the value of a pure substance is particularly high because you can have control over the interaction it has with its environments.

Electrical sense (similar to a magnetic sense). To sense either the voltage or amperage or Wattage (V*A) of an existing electrical system. To be able to determine the effectiveness of energy generation (i.e. from a solar panel) without other systems.

Radiation sense. Humans just don't feel radiation till its killing us; even then we don't know what it is (sometimes doctors even fail to identify radiation burns). Would be nice to have (even if I also wish it were less common to not be a sense needed)

A measurement sense for dimensions of size; weight; volume. To be able to get more than a subjective feel for a size of an object. Even after measuring things and writing them down; we still have to trust the ability of our measurement protocol. A classic line from woodworking is "Measure twice, cut once" but for me is "measure twice alone and a third time in front of someone else".

A dietary intake sense. To be able to determine the optimum food intake based on an expected future activity ratio. To automatically not have to worry about being overweight or underweight. Similarly an intuitive "need to exercise" sense (where with things like depression you are demotivated to exercise when it seems to often help).

A meme sense. A sense of understanding of when you are trapped in loops. (I have no idea how to do this other than the hard way)

A gas (or liquid) quality sense, to be able to check the composition of substances for their safety (particularly oxygen content, or presence of heavy metals in water)

(wow this is quite a few)

(Edit: Data processing senses would also be good, even a brain-cache to be able to record a few seconds of sensory information and then reprocess it over the next minute)

I had never heard of any of these except people putting magnets in their fingertips. Thanks for the post!

Minor typo I noticed:

"...and it is unique in that it is not implanted but instead." (instead what?)

Theoretically, the 'Love Hormone Measurement System' has some utility. We form bonds to others with every kind word and familiar touch, it may be useful for many different populations of people to gain a clear sense of how they really feel about "loved ones", and why that is.

Also a general purpose sense of whether a person has spent too long or too little in the sunlight might be very harm reducing. A lack of light can cause myopia, too much is cancerous...

For myself...maybe a sense of polyrhythms?

How about just another vision channel, but mounted on a remote scout, such as a robot, drone, dog, or hawk?

To feel upcoming seismic events.

I feel like there are interesting applications here for programmers, but I'm not exactly sure what. Maybe you could link up a particular programming language's syntax to our sense of grammar, so programs that wouldn't compile would seem as wrong to you as the sentence "I seen her". Experienced programmers probably already have something like this I suppose, but it could make learning a new programming language easier.

Re GPS, being able to "see" the GPS satellite constellations with the time delays encoded as color shifts would allow the subject to quickly learn to geolocate themselves.