MON, the app my ds uses is called "Formula"- you can find it at the app store by searching for "equation editor". It's not efofex by any stretch but it's still useful.
I just did a quick search to get the name of it (because he's at school and I can't remember without looking lol!)... and noticed there seem to be a *lot* more equation editors out there than there were just a few months ago when we first looked. You might find something more useful by looking around at the app store - I think I'll be looking later this weekend!
Best wishes,
polarbear
