This fall T-Mobile will add Wi-Fi calling to select Android devices, according to a leaked training document posted by TmoNews. The service operates similar to Skype on Verizon phones and will allow unlimited calling when connected to a Wi-Fi hotspot.
A tutorial will appear when the user first enables Wi-Fi on their device. Once connected, T-Mobile customers will be able to send and receive calls and messages over their local Wi-Fi network. The service is completely optional and customers will not have to make any changes to their existing calling plans.
There are limitations to the service however. Unlike previous T-Mobile phones which supported Unlicensed Mobile Access (UMA), Wi-Fi calling will not offer any hand-off to the carrier’s mobile network. This means that if you make a call and leave the Wi-Fi coverage area, then the call will drop.
No list of compatible devices has been released, but Wi-Fi calling is expected to only appear on newer T-Mobile phones like the HTC G2, LG Optimus One, Motorola Defy, Samsung Vibrant, and I suspect the Galaxy Tab.
If you own an Android phone on another carrier, there is still hope for Wi-Fi calling because Skype should be coming to all carriers later this year.