The Bobsled plug-in, developed by Vivox, needs to be downloaded first from the . Restart your browser and you'll see a little green phone icon next to your friends' names if they're available to chat.

A pop-up box lets you check your mic and speaker levels, and you're off to the races, provided your friend answers the phone. If they don't pick up, you can leave voice mail by clicking the Bobsled icon at the bottom of your chat buddy list.

According to , the Bobsled brand will expand to include other cloud-based communications services: "In the near future, T-Mobile plans to evolve Bobsled by T-Mobile to include video chat [and] the ability to place VoIP calls to mobile and landline U.S. numbers, and [T-Mobile] will offer applications on smartphones and tablets across various mobile platforms, regardless of the carrier that powers such devices," the blog reads today.