Surprisingly, I couldn't uncover any existing Haskell interpreter for Android.

But here are some instructions for writing your own interpreter for the Scripting Layer on Android. That's assuming you're willing to try mapping the haskell functions on top of the Java android ones (which is not a perfect solution, I know). You'll also want to refer to their scripting layer written for Scala, because that's the one that comes closest to Haskell (which is not very close I admit).

Otherwise, there shouldn't be any reason why any of those Haskell implementations couldn't be directly compiled for Android using the NDK. As long as they're written in C, they should work on Android. For C++, that's a little bit more tricky since Android doesn't have all the C++ headers.