Vox me! http://i.voxer.com/in205

Voxer is marketed as a Walkie Talkie application for iPhone, iPod Touch, iPad, and Android devices, but it adds much more.

Features Include:

• Live Walkie Talkie
  Voice
  Text
  Location
  Group Chats
  Photo Messaging
  Playback Capabilities
  Offline Capabilities
  

Messages are streamed live. Friends can participate live or listen to them later.

The Voxer team was part of the team that created the popular Danger Sidekick handheld device, and worked with Apple, Google, and Samsung.

Although many consider it a "plus" that all messages sent through Voxer are encrypted, it can allow abusive message to be sent that are difficult or impossible to track.

Of interest, Voxer's newest update just launched. Improvements include better audio performance on some devices and a dark theme option for easier viewing in low light conditions. Frozen screen and black screen issues on some LG and Motorola devices have also been fixed.