The android IMSI catcher detector is an android based project to detect and (hopefully one day) avoid fake base stations (IMSI-Catchers) in GSM/UMTS Networks.
With IMSI-Catchers being exponentially popular lately, and with an explosion of various "bastards" with governments and criminals all the same, using it. Anyone can now buy an IMSI-Catcher (or build a cheap one on his own). In addition they can all crack the A5.1-3 encryption on the fly!.https://github.com/SecUpwN/Android-IMSI-Catcher-Detector
Project size is around 85mb, it contains papers and ebooks about GSM protocols and related subjects, some papers are in German.