I've been working on this. I think I can reliably hit the quality ballpark of STT APIs at the acoustic model level, but not at the language model level (word probabilities) in a low-powered-way yet.

Also, non-English models are _way_ behind still.

The way google & now Apple manage to run these on device is pretty neat. Google has a blog post for the same too.

The recently updated Mozilla Voice dataset still lacks non-EN languages sadly.