I just published an Android app that lets you develop applications from your phone. It's a simple IDE with a script language and interpreter, visual screen layout, database management, etc. It's a v1 that has had a beta tester of just me, so beware.
You can review the Developer's Reference for a quick idea of what's what. And it comes with some sample applications for basic examples of what can be achieved.
(The marketplace is refusing to update images and text right now. Apologies if the copy editing is wonky.)