Use Cell Tower Tracking to turn GPS on/off

[dcattran]

Typical pattern of usage is that the handset is stationary in a single location (home, work, hotel, etc.) for a long time, then it's in motion for a relatively short time. (drive to work, client, airport, etc.)
My suggestion is that there be two modes, which I'd call "active" and "idle" mode. In active mode, it works the way it does today, tracking location, etc. If, however the location remains essentially unchanged for a long period of time (say 15 minutes, should be configurable) then it switches into "idle" mode. In "idle" mode, it would wait for a change in cell towers, and/or checks GPS location very infrequently (1/2 hour or something like that) to switch back into "active" mode. Of course should be a way to manually switch to "active" mode, on demand.
If it is relatively easy to determine what cell tower/towers the unit is in contact with then this shouldn't be a big development effort, much less than trying to determine location using that method.