https://www.noisebridge.net/images/9/91/Jne5_4_r02.pdf and https://en.wikipedia.org/wiki/Paul_Bach-y-Rita are probably what you're looking for.

This was a particular passion project of mine a while back. I tried building a haptic compass that could be worn on the wrist and discovered that that the actual haptics mattered a lot. Vibration didn't work at all for me (I couldn't internalise the feeling - however much the intensity modulated it just felt like buzzing) but ended up using a kind of trick of directional "tick" lines to represent proximity to North - which felt almost instantly familiar.

I never finished the project, but love this idea!

https://youtu.be/7UaAwTuahWo?si=YFBq1trurHq0P7i-

That's so cool! I can imagine it kind of feels like when you have a wheel that you can turn with your fingers and it kind of "snaps" into place at regular intervals, like your body rotation is snapping into a cardinal direction.

Have you thought about trying something similar using Android? Taking the compass and doing small short vibration blips, you can also pair them with sound and light for testing or reinforcing it. Although I can imagine that the compass is not very accurate and the vibration control on Android is probably all over the place in terms of consistency between devices. But being able to have it as something compact that you probably already carry around could make it real-life useful.

I can imagine it being an assistance when it's in your pocket and it passively keeps feeding you the blips, you could use the proximity detection to make it only do that when in your pocket, for instance.

Reminds me of when people used to get magnet implants in their fingers so they could sense electric fields.

People are still doing this and although results may vary significantly from person to person, there is actually utility to it. One friend of mine was saved from electric shock during his work on multiple occasions, thanks to his extra sense. Bioproofed neodymium implants can even be sourced from shady Chinese vendors at a very low price, indicating a certain level of demand. The only hurdle is finding someone willing to operate on you; some tattoo shop backroom is often a solution...

I don't think that present resolution would be good enough for me ;) - I wish an option with small matrix of tiniest, more sensitive magnets, maybe of varying (resonance) sizes ?

As a touch sense extension it seems intuitive to adapt - but feeling it more like a sound or colors, less as vibration then.. ?

What about inducted solution - like a matrix of nanocoils calibrated to/messing with nearby neurons electrical levels to provide super precise feedback - or to feel it maybe like different keys being focused to press by mm movements ? ( reverse keyboard ?? )

I vaguely remember one of them being sad after the experiment ended, since it felt like they lost one of their natural senses. Slight ethical concerns were raised, afair.

Would be cool to build one into a baseball hat.

Or even put an array of car parking proximity sensors into that hat. https://www.kit.edu/kit/english/pi_2016_003_feeling-spaces-w...