T-Mobile slid head-first into the social media world today with the announcement of Bobsled, a new brand for online voice and data services. Bobsled for Facebook, the first in a planned series of new products, is a downloadable app that works inside Facebook to allow you to place voice calls to your friends via the site's chat system. With Bobsled installed, you just click on a phone icon next to a friend's name in the chat menu and you can place a Skype-like voice call to them whether they have Bobsled installed or not.

But perhaps even cooler than the calling feature is the ability to post voice messages. Bobsled allows you to leave recorded messages on your friends' walls that can be either private to them or public-- your call.

Bobsled will be coming as an app for Android and iOS soon. For now, the ambitious new program is wisely leveraging Facebook and its 600 million users-- a market where competitors Skype and Google Voice have yet to establish a presence.