Another really nice ukulele chord app is "UkeChords" ($1.99). When loaded on my 3G iPhone the keys of c# and f# don't show up as options but they are really there--you jus' press on the empty space where they should be. I'm sure an update correcting this is on the way.
Ukulele Chord Kumu is prettier and better executed, UkeChords is (far) more comprehensive in its chord dictionary but glitchy in its execution. Neither one is everything it should/could be.
Craig My goal is to be able to play as well as people think I can.