iWhiteBoard is a mobile substrate extension that allows you to draw on any app, even 3D games, YouTube, and live camera images, etc. This app has limitless uses. Just shake to activate it (Activation method is changeable with Activator). Once enabled, you can draw anywhere. Double tap to pick from 4 colors and triple tap to clear. To disable, just press the home button or shake again.
Set/change the activation method by using Activator’s configuration panel in Settings app.