Just wanted to say thank you for this. I was able to implement it in a matter of minutes with one of my older projects I wanted to add achievements too. I had previously used CocoonJS to wrap it for iOS, but it doesn't have achievement support yet.
Anyway, my only issue right now is the sound engine doesn't seem to start until the first sound is played, so it's delayed a bit, after that all is fine. Seems to be an issue with with CocoonJS, Phonegap and Ejecta so I'm not worried about it.