I know Python apps are faster to write, but it seems Java is the 800 lb gorilla for mobile and  GUI development.
Are there any mobile platforms that run Python, or should I go the Java route?
The first question is whether you really need to develop an app, which requires per-platform work, vs a webapp.
If you really need an app, then you might likely need a separate language for each platform! For Android you'd want to use Java, and for iPhone/iPad you'd want to use Objective-C. A good argument for really trying to go the webapp route.
Python or Java? Whats better for mobile development, and GUI applications