TalkBox for Blackberry is available for beta download. The app is considered to be a voice chat app/walkie talkie. I think of it as a glorified voice mail app kinda. You can send voice messages to people all over the world. Or even do a voice post on Twitter or Facebook.
Get the beta download here. For devices running OS 5.0 and up. There are a few questions you have to fill out but it shouldn’t take long.