Have you heard of Bump? They were doing something similar until they were acquired by Google: https://www.theverge.com/2013/9/16/4736860/bump-acquired-by-...

They're basically the Google Photos team, now. Have you seen the ads about face recognition and auto-sharing? They've been working on the problem of photo sharing ever since they figured out that people didn't want to share contact info with Bump, they wanted to share photos.

Didn't know that but makes a ton sense. Also surprisingly how Instagram became Instagram when they realized all it was being used for photo sharing. People love their photos.

Can you go into more detail with how that worked?

Not OP, but I'm guessing signal strength measurements, so if 2 devices report similar values they must be close to each other. And then just add the gyroscope info.

That's an interesting suggestion. I'm curious if the body position as it relates to the closest antenna and the phone, particularly if the RF energy has to pass through the owner's body, would add too much noise when compared to the person if they're standing facing the closest antenna.