Brilliant idea!

But hard to believe though it may be, T-Mobile did make an announcement last week. And even harder to believe, its new product may be as game-changing as Apple’s.

It’s called T-Mobile HotSpot @Home, and it’s absolutely ingenious. It could save you hundreds or thousands of dollars a year, and yet enrich T-Mobile at the same time. In the cellphone world, win-win plays like that are extremely rare.

Here’s the basic idea. If you’re willing to pay $10 a month on top of a regular T-Mobile voice plan, you get a special cellphone. When you’re out and about, it works like any other phone; calls eat up your monthly minutes as usual.

But when it’s in a Wi-Fi wireless Internet hot spot, this phone offers a huge bargain: all your calls are free. You use it and dial it the same as always — you still get call hold, caller ID, three-way calling and all the other features — but now your voice is carried by the Internet rather than the cellular airwaves.