Hello All,
surfing occasionally through Google Play I am noticing that two-way radio style apps are coming as mushrooms. Looks like two-radios epoch is coming to down. Most of those apps are pretty simple so far, but some looks good. I tried Walkiefleet and what was good is that they have Windows based server and Android as the client. Calls through 3G or 2G are intitated slow sometimes, but eventually operators will improve their infrastructure. So I guess two-way radios will go to the past soon 
Yeah, tried a few. They can use their internal wifi frequencies to transmit voice.
WalkieFleet is very good in my experience.