Nothing much to say, it uses your phone's inbuilt vibrator and you can set it to vibrate at your desired frequency and intensity.
*Note, some phones have really weak vibrators, so usage experiences may vary.
Just realized this had just under half a million downloads! Will provide regular updates from now on.
1.1 - Small bug fixes and added a splash screen
1.2 - Used toggle switch instead of toggle button cos it's prettier.
1.3 - Minor bug fix
1.4 - Added running under lockscreen, for obvious reasons ;-)
1.5 - Made the sliders bigger for easier control
1.6 - Fixed Windows Phone 8 bugs
Fixed Windows Phone 8 auto crash bugs