That's pretty much exactly what python-on-android does; the problem is that you don't get access to any of the Java/Dalvik-based libraries, which includes all of the UI programming libraries.

Couldn't a language-bridge library use Java reflection to accomplish a lot of what's needed?

That is already done with pyjnius. The missing part is providing more pythonic and more productive ways of using it. Currently it is extremely awkward...

My guess is that someone will write a pythonic UI framework based on the Android API...

Do you mean you want something like Mono's Xamarin in Python?

It's a possibility – Qt's there, and in fact Kivy is a pretty good solution.

The problem I raise in the talk is that such libraries will always lag behind the state of the art for Android GUIs, which makes them less attractive.

Ah I see. This is the old issue. Why wrapper layers have to be later than its source…

The Kivy lead developer has just recently been working with native Android widgets in python-for-android. Stop by #kivy on Freenode and ask tito about his Google maps demo.