I think that bringing Bitmessage to smartphones is probably one of the best ways of getting this protocol into the public space.
However, don't take this the wrong way since I do like the concept, I feel as though a seperate service to send/receive/work messages detracts security, or at least some anonymity, from the network. Not that it could be the case, it's just how I feel.

I would still love to see this come to fruition though.
I'd like to see the offering of more options like local PoW on the user's device (I know ARM isn't that powerful, but it's not Bitcoin mining) or their remote machine with BM PoW software installed, such as a home server.

Also, will you be writting the client in HTML5?