Checkout Kivy. They have done a really great job so far, and I am a big fan of their work. It is still lacking some providers, but they keep adding new stuff to it everyday. First thing you need to do is to check your requirement against what they can offer based on their documentation. They have create an amazing framework for input such as multi-touch or pen handling. They use OpenGL ES internally, as a result complex graphics and visualizations can run very fast when interacting with the the application. Their process for creating an apk is also very straight forward.