Cingular is now joining the Push-To-Talk party. Cingular's service is pretty basic, though it includes simple conference calling and a "Buddy List" that lets you check if the person you'd like to call is around before you go ahead and expend the energy to push that button. It also includes an easier way to switch a PTT call through the cellular network. Right now, you can get the service on the LG F7200. Also look for the Samsung D357 in the near future. Looks like it should cost about $9.99 per line for national plans and $19.99 for all lines in a Family Talk plan.
Cingular Launches PTT Service [Mobileburn]