Just enter a verb in its infinitive form (e.g. 하다, meaning "to do") and youll be presented with the many different forms of the verb, all correctly spelled - 했어 (past), 하겠어 (future conditional) and so on. No more having to check with a native speaker when writing unfamiliar verbs!
The app doesnt have a dictionary of verbs; instead it actually understands the rules that govern how all Korean verbs are formed. It explains how each verb is formed, which is a great learning aid.
Theres also a web-based version, the full source code and more at http://dongsa.net Dongsa is by Dan Bravender with this iPhone version by Max Christian.