jg99 CellMapper is fine when you run it while in motion (on a drive, train, bike ride or hike for example). It does drain battery faster than if not running, but not drastically so.
Don't run it at home or work, all the time, or when stationary for more than a few minutes. Too many logged points at one location actually messes up the map (makes coverage patterns appear to only serve that location and nowhere else).