I think the new QT mobility stuff would make this VERY easy (specifically the interface with the actual sms system). But I think it is not so useful without the T9 stuff (the predictive text where you don't have to hit a key multiple times). To be uber-geek, I would like to see this with a keypad option and a morse option--a few years ago there was talk of morse being as fast as (or faster than) 9-key text entry.

I wish I had the free time to play with it, but it wouldn't get out of devel until 1.2 appears anyway so it could use the new mobility stuff.