Illegal ? I don't understand. PilotAware transmissions aren't illegal anywhere in Europe.
It receives ADSB and other PilotAwares and transmits to other PilotAwares.
Bit like Flarm, but with a greater distance/higher power.
Distance is quoted as 20km for the PAW signals, but some of us are seeing other planes a lot further out than that.
ADSB you can obviously pick up a 100 miles away !
Anyway, there's a much more in depth discussion of this going on over at the PilotAware forum, where the invite was also posted.
(Including what constitutes the "lower end of GA" and if your aircraft qualifies as such)