It is based on an Arduino, a GSM modem and a small NRF board for the wireless sniffing. All that packed in a standard USB charger case. All the code is available in gihub.
Even when it is a bit old, I think it is a great example of HW hacking. Take a look to the code to figure out how some stuff work… how to send data via an old GSM modem, sniff RF signals,…
@pry0cc you’d think it would be interesting to kick off a community project involving HW?.. Maybe start with something simpler that this keylogger and go further step by step