Small sensor for detecting GSM man-in-the-middle attacks, otherwise known as IMSI catchers and Evil BTSes.
Uses R-Pi2 or 3 (Odroid works fine too) along with an RTL-SDR (inexpensive DTV tuner) and a GSM modem to detect anomalies in GSM bands.
Project page: http://sitch.io
Sensor code: https://github.com/sitch-io/sensor/tree/v2.0
Stick to the V2.0 code for now. V3 coming soon, and the stuff in the master branch is in a state of transition.