OpenSignal - Mobile analytics and insights on wireless connectivity from Opensignal, the independent global standard for understanding the true state of the world's mobile network.
OpenCellID - OpenCelliD is the largest Open Database of Cell Towers & their locations. You can geolocate IoT & Mobile devices without GPS, explore Mobile Operator coverage and more!
CellID Finder - Find a cell phone location using LAC/CellID, GSM BTS coordinates
wigle.net - WiGLE (Wireless Geographic Logging Engine)
Android IMSI-Catcher Detector - Detect attacks of fake base stations such as IMSI-Catcher and StingRay on your GSM/UMTS network.
GSMmap - This app collects GSM security data and adds it to the GSMmap web site.