geofence
n.— «The technology causing a stir is called “geofences,” and here’s how it might work: A struggling salesman veers off his route and slinks into a bar. Within moments, his boss knows he’s there. The bartender didn’t rat him out. It was his work-issued cell phone. By bringing it inside, the phone crossed a computer-generated “fence” drawn around the bar by the boss.» —“Your cell phone could bust you” by Shamus Toomey Chicago Sun-Times (Illinois) Nov. 27, 2005. (source: Double-Tongued Dictionary)