Android Apps for GSM signal analysisGSM Field Test 
Logs signal strength and geolocation viewable live as a big fat line of dots on a google map. Logs are downloadable as kml files.
Shows GSM dBm or WIFI strength on a meter and shows info on cell tower locations, your IMSI and other details about your phone and network. Also logs info downloadable as kml files.
Another RF signal app
Web based tools
Open Cell ID 
GSM Signal strength heatmaps, base station locations, API and Android app.
Wardriving thing that also shows GSM info.