The cell phone is probably their most widely used two way. Everyone rants and raves over stuff like Fedcom and stuff and there is stuff out there, what little isn't encrypted, but not too long ago when the DHS head (i can't pronounce her name, Janet something) came to Nashville the USSS was her detail. When they were on the move the report that they were on their way wasn't by radio but by the USSS agent at the aircraft answering his cell phone with the news. I was standing right beside him.