They were teased nearly a year ago, and now they’re here: T-Mobile’s HotSpot @Home wireless plan offers customers new Unlicensed Mobile Access (UMA) phones that can alternate between T-Mobile’s cellular network or a home wi-fi Internet connection.

This isn’t like having a cell phone that also happens to work as a cordless phone. You have the same number, whether you’re on Wi-Fi or cellular. And in an engineering feat, the new phones will hand over calls that are already in progress from Wi-Fi to the cellular network if you leave the hotspot, so you can start a call at home and then keep talking as you walk out.

My original concerns about wi-fi leeching being the basis for these for these types of phones seems unwarranted. It’ll be confined to a single wi-fi access point, presumably the customer’s home; anywhere else, T-Mobile’s standard connection takes over.

I’m thinking this will be a tough sell, simply because the concept will be difficult to accurately communicate to the average consumer. Positioning it as a supplement to spotty coverage is a good starting point. Maybe their “The Only Phone You Need” campaign will get it across, but I’m not sure it’ll completely resonate.