[alansk]

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.

[chriseidhof]

Yes, that's with.me and hashable, they do something similar. Also Noteleaf does something like that.