This app was mentioned in 2 comments, with an average of 2.00 upvotes
I worked on PGI GlobalMeet, a bunch of stuff that never really went anywhere (I worked in a third party dev house for a while), and most recently did Phone Beacon, and anti abduction app that is kinda handy for Pokemon players.
Certainly nothing even close to this scale.
For an added layer, check out Phone Beacon