Some vector drawing tools. Fountain Pen tool. Allows exporting the drawings to SVG format which can be imported easily with more complex vector design programs like for example adobe Illustrator.
Don't forget to visit section "basics" of the website in play store app's page. That and the tutorial into the app should be enough to start working with it.
With the use of a pointer, the precission you can reach drawing with the finger is similar to drawing with a mouse. You can also connect a mouse to your device and handle it as a desktop app.
New! Now you can import svgs from any app or program as long as every object is transformed into path. Visit app's website for more info.