One of the best features of many T-Mobile phones is the ability to call people via WiFi. Why would you want to do this? Well, mostly because it doesn’t rely on your sometimes finicky mobile connection, instead using WiFi to place calls. Most can imagine why T-Mobile users who had it previously would be a little upset over not having it work properly on their favorite ROM.
HTC Sensation users have faced this problem. Luckily, however, it has been solved for both AOSP and stock ICS ROMs. The apk was modded and re-released by XDA Senior Member bigmoew for users to have in case their ROMs didn’t already come with it and for developers to include in their ROMs should they want to include it.
The app comes in the form of a recovery-flashable update.zip file, so there’s no difficulty in installing it. However, users must first remove any previous versions of WiFi calling they may have installed. Installation through recovery is required because it includes libraries required to make it run properly, which is especially true for AOSP users. And because there are two versions of the app—one for AOSP and one for stock—practically all Sensation owners on ICS can join in on the fun.
For additional information, hit up the original thread for all the download links and instructions.