T-Mobile plans Wi-Fi calls using dual-mode phones

According to the WallStreet Journal, T-Mobile plans on offering cellphones that can roam on Wi-Fi hotspots, with the goal of improving indoor reception and help customers save on monthly cellular minutes. When a user comes in range of a WiFi hotspot, a connected call is automatically transferred onto the Wi-Fi network, with no noticeable change for the user. This of course requires a dual-mode handset. The service, known as Hotspot at Home, has been in trial in Seattle. Phones for Hotspot@Home, supporting both Wi-Fi and GSM cellular, include both Nokia and Samsung. Of course, Wi-Fi is a well-known battery killer, even when a device isn’t in use, although T-Mobile claims they've licked the battery problem.
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\nBut here's the kicker - it's an additional \$20/month to use the service, with a \$5 additional monthly fee to add another family member. Who the heck wants to pay that much money just for the ability to be able to seemlessly roam to a WiFi hotspot and save on using your monthly wireless bucket of minutes? You'd have to be a very heavy cellphone user. In fact, you'd have to go above your allotment of monthly minutes often for this to make much sense. But if you do go above your monthly minutes and are paying the overage charges (high per-minute rates) you should be changing your plan anyway to include more bucket of minutes. In any event, Hotspot@Home is set to go nationwide in June. I think T-Moblile needs to make a more compelling case for this feature before they start charging such ridiculous pricing. Just MHO.