4n77r4xX: No such thing can exist--if you radiate a signal, you can be tracked with it. Period. Even without GPS your signal can still be triangulated, especially within a city with small cells. Likewise, anti-tap is a misnomer since calls and such are tapped at the switch, not over the air. If you're talking about that software (hardware?) to use your phone as a bug, that's a whole other level that requires device access of some sort.

Markosib: There are a couple of problems with directly accessing the cell radios (regardless of technology).

1. There's unlikely to be direct connections between the main processor and the radio's due to fraud potential. This is why the N900 and Neo Freerunner have external, self-contained radios.

2. 600mW is way above the Part-15 unlicensed limit for the 900 MHz ISM band here in the USA; I'm assuming that's true elsewhere this band is available. The FCC or its equivalent in other countries would definitely come calling. This band is also used by licensed hams in the US and Canada as well, so you could get away with the higher power limits if you could ID properly and meet the requirements of the service (no crypto, no bad words, no music, no commercial use, etc).

Note that I'm not against any of this from a tech standpoint, and Serval looks very interesting! However, the potential for abuse of the band (if the cell radio is used) is high. OTOH, if they strictly use the unlicensed bands within their power limits, or with higher power limits within their political limits, this could be wonderful! (Of course, if you're routing around nasty abusive government controls, then all bets are off!)