Officially, like other wireless carriers, T-Mobile charges for tethering or using your phone as a Wi-Fi Hotspot--$14.95 a month. Unofficially, however, many T-Mobile users have been able to share the data plan on their cellphone with their computer over Wi-Fi or with a USB cable without incurring any extra charges. This free pass may be coming to an end with the Android 4.0 ("Ice Cream Sandwich") update.
The mobile hotspot/tethering feature on T-Mobile has been free on some smartphones but not others. On my Galaxy SII, for example, the Portable Wi-Fi hotspot feature doesn't work because I don't have that $14.95 plan. With my husband's HTC Sensation, however, we can use the Wi-Fi hotspot feature to bring our Wi-Fi only iPad online wherever we are--for free.
PC Magazine quotes a T-Mobile rep confirming that the company will start enforcing a $14.99 smartphone mobile hotspot plan when HTC upgrades their phones to Android 4.0 on Wednesday. Bummer!
Paying for tethering or a version of tethering, Wi-Fi hotspot, sucks, frankly. You're paying twice for the same amount of data in most cases. Many of us want to use tethering only in emergency backup cases, not regularly enough to warrant spending $15 a month more on our cell phone service.
You may be able to get around the extra charges, however, by rooting or jailbreaking your cell phone and using a tethering app instead of the default carrier-approved tethering method. Some carriers block you from installing tethering apps from the Google Play Store or iTunes, however, so if you see one up there, time to install right away while you can.