Do also check out the new option in Settings (TrackRec's settings in the iPhone settings app... ). The new "Cell tower triggered" will disable the GPS and trigger location updates only when there are significant location changes. These updates are typically far less accurate than the GPS updates, but this mode might still come in handy for example if you want to have location sharing always on (without draining the battery).
While on the Settings topic: the old "Distance filter" setting wasn't really working as it should. That should be fixed now.