I couldn't find a good app for playing mp4 videos at double speed on iPad, so I decided to create one myself.
With PlayX2, you can choose from playback speeds of x0.25, x0.5, x0.75, x1.0, x1.25, x1.5, x1.75, and x2.0.
You can install PlayX2 here.
PlayX2 - an app for easily playing videos at double speed
