I mean check-in technology is at least as old as dodgeball (foursquare predecessor acq by G). G + FB both have check-in based features. gps includes altitude (

I mean check-in technology is at least as old as dodgeball (foursquare predecessor acq by G). G + FB both have check-in based features. gps includes altitude (albeit gps isn't that precise in cities). phone geo can use cell tower triangulation + wifi scanning, on both aapl + droid, whether or not you connect to wifi. i.e. they have lots of ways