To all T-Mobile subscribers with DSL at home, HotSpot @Home is an add-on service that offers unlimited voice calls nationwide from your house configured as a WiFi hotspot or at any of T-Mobile’s HotSpot locations all over the country. When you are making a call and you go beyond the range of the WiFi signal, your call will be handed over to T-Mobile’s cellular network seamlessly (without you knowing it) and then from that moment, the call duration will be deducted from your voice minutes (supposedly).

I said supposedly because that should be the case for billing purposes. However, an article from David Pogue of the New York Times mentioned that that is not the case. You can make unlimited calls if and only if you initiate your call from a WiFi hotspot (like from your home or at any of T-Mobile’s HotSpot locations) regardless if you are within the range of the WiFi signal, or you go beyond its range and effectively being handed over to a cellular network. So for example, if you are at Starbucks and you got a call from a friend, you can walk to the parking lot, get into your car, talk all day, all night, and need not worry about burning your monthly plan voice minutes!

On the other hand, if your call is initiated from the cellular network (that is, the ordinary mobile call you make when you’re on the road or at school), your voice minutes from your monthly plan gets deducted even if you reach home or at a T-Mobile HotSpot hotel, for example.

That is the case for now unless T-Mobile change its billing system.

For those who are not in the know, your calls nationwide are being transmitted over the internet but this time using wireless technology called WiFi. In a way, T-Mobile HotSpot @Home competes with VoIP companies such as Vonage, SunRocket etc. T-Mobile is basically telling you to get rid of that landline from your house which is good because you save  and you are mobile. Talk about mobile VoIP.

But more than VoIP, it lets you make calls without having tethered to a computer/headset combo or ordinary telephone equipped with VoIP adapter at home. Instead of getting another VoIP number, you get a mobile number but doubles as a VoIP number as well all in one cellphone. However, unlike Vonage, you can still make unlimited calls at T-Mobile’s HotSpot locations like Starbucks, FedEx Kinko’s, hotels and major airports nationwide, or even abroad. If you are on a WiFi-enabled hotel abroad (or any WiFi hotspot for that matter), you can still make unlimited calls to the US!

Hotspot @Home comes with a wireless router and 2 WiFi phone models to choose from: Nokia 6086 and Samsung t409 (although T-Mobile plans to make all their phones WiFi-compatible). It is available for individual plans with $39.99/month or higher, and FamilyTime plans as well.

Detailed review is available at BusinessWeek.

And oh, one more thing: Just don’t confuse T-Mobile HotSpot unlimited internet access with HotSpot @Home which is about unlimited voice calls. Did I also mention that you don’t need to carry your wireless router? (just leave it at home).