You might also want to look at JNative (on sourceforge, IIRC) that
gets rid of some of the JNI complexity when accessing functions in a
shared library. Not sure if android apps can include a .so, but since
linux system functions live in known shared libraries it might be
useful for those.
I haven't looked at how the NDK handles binaries for different Android
platforms, although I suppose most every target is ARM of some flavor.
Eric