Tremor for Android
Gives you almost 100% control over the vibration of your device! Constant Mode is not stopped by other operations on your device. It continues even if the screen turns off, or goes into standby mode. Variable Mode however, is best used when you don't plan on being disturbed, such as by setting your device to flight mode. Check out the tutorial on the developer site - quick and easy to read.
by G####:
To get the most out of this App, be sure to see the tutorial on the developer website.