Android (finally) supports more than access just
to Google's JVM, but that is the mainstay and most stuff is written in Java.
There are other runtimes available through the NDK [link
], which gives access to C/C++ and through that the ability to build compilers for whatever else (there are a few experimental ones for languages like Haskell). If you face performance constraints and already know C++ its an option, but you might have to port/rebuild your favorite libraries.
There are more options available when it comes to Java-related languages like Clojure and Scala. Of the two, Scala is the more practical choice simply because Clojure takes forever to initialize (this is supposed to be fixed soon, or may already be, but as of today it loads slow).
The complexities of dealing with languages other than C, Java and Scala tend to practically restrict development to those languages. And that's really
not a good way to guarantee a long future for the platform, so I expect more environments will become commonplace in the future.