TMobile has introduced new cell phones that can use your home's wireless internet connection to make and receive calls. The technology is called UMA, or unlicensed mobile access. It does cost an extra $10 a month, but you might be surprised to know that they don't count those minutes against your plan. So, depending on how often you use your phone at home, you can move to a lower cost plan and save way more than the $10 charge.
To use Wi-fi calling, you do need a special phone. Most of these work seamlessly bettween GSM cell phone signals and Wi-fi, but save you minutes off your bill by using Wi-fi when it is available. Some of the phones come free with your plan, but the high end phones, like the Blackberry Curve will cost you. It's also a handy technology if the cell phone coverage in and around your house is weak. The phones will automatically select wifi if it's there. Additionally, the phones use wifi in T-Mobile hotspots like Starbucks with no configuration necessary.
The same technology can be used at home on your PC with just a USB and a headset with many free VoIP services. You can get a wireless headset for less than $20 and use it to make phone calls whenever you are at home. There are also Wi-fi phones without GSM ability that cost no monthly fees. You just turn them on and talk as long as a wireless Interent signal is available. These devices, however, cost about twice as much as a headset. On the plus side, they are often equipped with additional features like an address book and PDA functionality.