From what i understand it uses the accelerometer to create a "bump signature" and matches the two devices according to that. The geo-location thing only helps filter that search and i think they introduced that part later on when they got a huge number of users across the globe.
Now what is note-worthy here is that the signatures wouldn't be "identical". They may not even be opposite as i think the idea is to bump your HANDS while holding them, so the hands may distort the vibrations. So the fact that they actually managed it to WORK is astounding.
Now what is note-worthy here is that the signatures wouldn't be "identical". They may not even be opposite as i think the idea is to bump your HANDS while holding them, so the hands may distort the vibrations. So the fact that they actually managed it to WORK is astounding.