Project is at https://github.com/google/j2objc. Has anyone used this in production? I'm normally wary of codegen/translation but this sounds like a good way to do Android+iOS without going to something like Xamarin.
I played around with it a few months back (I'm working on something similar but substantially less complex), and while it does sort of work, the output is hideous, and is more of a starting point than usable code. As of when I tried it, running it on itself produced an uncompilable mess.