AT&T might be dominating the headlines with its “revolutionary” iPhone this week but let it not be said the folks at T-Mobile don’t know a thing or two about revolution themselves.

The carrier has announced its “T-Mobile HotSpot @Home” service, which will allow for seamless WiFi/GSM hand-off for phone calls.

Here’s how it works: you buy either a Samsung t409 or a Nokia 6086 and T-Mobile will send you either a Linksys or D-Link router that acts as a standalone wireless hub or network add-on for your home domicile. Once you’ve got that all set up, you’re free to talk–calls will automatically route over the WiFi network when available (either at home or when close to a T-Mobile/Starbucks hotspot) and will seamlessly hand off to T-Mobile’s network when out of WiFi range.

Want more? There’s no charge for calls originating from a WiFi connection–even if that call is later handed off to the network (T-Mobile charges a $10 monthly fee for using the service).

Does it really work seamlessly? According to Engadget Mobile, not really. But that doesn’t mean the service is not without its merits. “Setup was a snap, the phone’s basic but well-designed, GSM / WiFi hand-offs were hit or miss, and for 10 bones a month, it seems like a square deal,” reported Engadget.

This could be an ideal solution for folks with bad reception at home, people who use their mobile as their primary phone and the double mocha latte with whipped cream crowd.

For more on T-Mobile’s HotSpot @Home:
– see this press release
– see this Engadget Mobile hands-on