T-mobile has launched their dual-network GSM / WiFi service (otherwise known as UMA). I was lucky enough to test this out in the beta period, and have to say that it is one of the most revolutionary things to happen to the phone in years.
There are only 2 phones out that currently work with this system (Samsung t709 and Nokia 6136) which will both be for sale for $50 with 2 year contract. I used the t709 and from a Blackberry users point of view, it is highly lacking in features.
It does however have WiFi, which is the main source behind this new technology. Let me see if I can explain how it works.
You are at home with your router (the included D-Link or your own) and you make a call with your cell phone. This call (and any other) that you place on any WiFi location (including T-Mobile hotspots) are 100% FREE. You need to leave but don’t want to hang up, so you simply walk out to your car and drive off. Once you are outside the range of the WiFi the cellular network takes over the call seamlessly.
The call using the cellular network is charged at your regular rate. This UMA service is an additional $20/month on a qualifying ($39+/month) rate plan.
With this service you can all but get rid of your home phone. There is no need to keep a home phone, when your cell phone provides unlimited calling while at home, Starbucks, or anywhere else that has WiFi.
The phone automatically picks up new WiFi locations and connects (even mid-call) to switch the call back to a free one. The clarity and phone quality is just as good as any VOIP phone I’ve used.
The new Blackberry 8800 (coming soon-ish) is slated to have WiFi, and hopefully will allow this Hotspot @Home service. A number of other T-Mobile phones (SDA, MDA, Dash, etc) already have WiFi, but no plans to release the UMA software in these WM5 phones has been released yet.