http://techcrunch.com/2012/02/21/att-launches-enhanced-push-to-talk-smartphone-trial-for-businesses/

I used to have active PTT functionalty on my old ATT branded HTC smartphone, but rarely used it. There are free apps now, such as Voxxer for iOS (e.g. iPhones & iPod Touch) that work like a walkie talkie, and don't add any extra cost on the monthly wireless bills. Presumably though, the above system may require both parties to have smartphones with the appropriate hardware/software to run the advanced PTT service. IOW, one of the older 'dumbphones' may not cut it any more. I wish I knew more about what they plan on rolling out. Definitely check howardforums.com for more details if you get a chance.