If you have one of the latest versions of iOS, use “Cherkalka”.
The app for drawing and storing sketches with cool interface and lag-free work. Works on all devices: from the 1st generation iPhone to the latest iPad with the Retina display and iPhone 5.
Drawings from the app can be saved to the clipboard and Photos.
This app is not a graphics editing program, but "paper and pencil" in your device.