• contributive database of cell IDs http://opencellid.org/
• find the frequency in fonction of the country / the operator http://spectrummonitoring.com/frequencies/
• report on the evolution of the gsm network an potentiel threats http://gsmmap.org/

From F-Droid

• Android-IMSI-Catcher-Detector https://secupwn.github.io/Android-IMSI-Catcher-Detector/
  • https://f-droid.org/repository/browse/?fdfilter=gsm&fdid=com.SecUpwN.AIMSICD
• SnoopSnitch https://opensource.srlabs.de/projects/snoopsnitch
  • https://f-droid.org/repository/browse/?fdfilter=gsm&fdid=de.srlabs.snoopsnitch

From Google play

• Stingwatch (seen at IFF) https://www.stingraymappingproject.org/
  • https://play.google.com/apps/testing/org.stingraymappingproject.sting_watch

• RTL_SDR : DVB-T dongles based on the Realtek RTL2832U can be used as a cheap SDR http://sdr.osmocom.org/trac/wiki/rtl-sdr
  • A nice software to listen to frequencies on Linux and Macos : GQRX http://gqrx.dk
  • For other softwares / OS, see http://sdr.osmocom.org/trac/wiki/rtl-sdr#KnownApps
• http://www.rtlsdr.org/start
• http://p-node.org/doc/index.php/Rtl_sdr
• Shop in France to buy the good device https://www.passion-radio.com/fr/recepteurs-sdr/recepteur-sdr-88.html

• BladerRF http://www.nuand.com/
• HackRF : HackRF One from Great Scott Gadgets is a Software Defined Radio peripheral capable of transmission or reception of radio signals from 10 MHz to 6 GHz http://greatscottgadgets.com/hackrf/
• USRP : Different products of Software-Defined Radio devices that can cover from VLF up to 6GHz http://www.ettus.com/
• GENESIS : NSA toy https://en.wikipedia.org/wiki/File:Nsa-ant-genesis.jpg from ant division
• PSDR : portable HF/Shortwave Software Defined Transceiver https://www.kickstarter.com/projects/1703258614/psdr-pocket-hf-sdr-transceiver-with-vna-and-gps

More artistic :

• Detektor : Martin Howse http://www.1010.co.uk/org/detektor.html
• Limen : Mario de Vega and Victor Mazon http://r-aw.cc/-/devices/limenia/
• The Electrosmog Detector - MW1 : http://emfield.tripod.com/

• Using Gnuradio http://gnuradio.org
  • Live USB stick : http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioLiveDVD
• To record and decode GSM signals : gr-gsm https://github.com/ptrkrysik/gr-gsm/wiki/Usage
  • which can be combine with wireshark https://www.wireshark.org/ see https://github.com/ptrkrysik/gr-gsm/wiki/Usage:-Decoding-How-To
• SITCH : Situational Information from Telemetry and Correlated Heuristics, software and hardawre to monitor GSM networks http://sitch.io/

• https://seaglass.cs.washington.edu/

• YouTube Tutorial: Building a Passive IMSI Catcher with an RTL-SDR