I had the same question, one app, one IDE all mobile platforms and I came across
memeapps[
^] when I first found it, it was just an idea and I've been following it on twitter. Now it reports you write the app once and it works on Windows mobile and Android with IOS and Blackberry to follow. its also free to download and use (Unless you require support).
I'm no expert and it doesn't really answer your question but I thought it might be another option to look at.
/Darren
P.S. I don't work for or have any alignment to memeapps just an interest in the original idea.