I was on a presidential detail a few times, and was surprised that they were using Nextel's direct connect for most of their comms then, about 3 years ago. Only a few times did I see anything bigger come out.
Frequency hopping and spread spectrum radios have been around for a long time - and I think that the military uses them extensively - which is why NEXTEL does sound like a good choice to me - but does that mean that every agent has to carry 2 radios? - ugh
I was on a presidential detail a few times, and was surprised that they were using Nextel's direct connect for most of their comms then, about 3 years ago. Only a few times did I see anything bigger come out.