I came up with a similar idea independently - except it was more of a social game (with foursquare-esque achievements). I envisioned a mechanism for confirmatio

I came up with a similar idea independently - except it was more of a social game (with foursquare-esque achievements). I envisioned a mechanism for confirmation of the rendezvous whereby both parties run the app and agree the meeting occurred and their proximity is verified. That's about as far as I got. Edit: looks like with.me did the closest thing to this already.