UkeMaster for the iPhone is a continuation of Sheep-Entertainment's Ukulele Chord Finder on the internet which has been well known since 1998.
You can choose your own tuning, D-tuning, C-tuning, baritone and more. You can also easily tune your ukulele using the pitch-pipe.
UkeMaster helps you to find both basic and advanced chords, more than 40 chordtypes in total. Basic and advanced chords are colored different so you can easily distinguish them.
You can find more ways to play a chord anywhere on the fretboard by clicking the hand. First the most basic fingering is shown after clicking a chord-type or root-note. By clicking the hand you will find fingerings higher up the fretboard.
The found chord shows you the relative note for every finger-position. This way you learn how the chord is built and teaches you how to built chords yourself. The root-note of the chord is labeled as 'R', the others show you the name of the interval relative to the root-note.
Different chords often overlap. For example C m7b5 can be the same fingering as D# m6. By clicking the chordname you can loop through these chords and see how they are built, eg. where is the root.
You can also find chordnames by clicking positions on the fretboard and see which chord they make. This way you also learn how chords are related to each other. For example start with a C7, click one fret above 5 and get a C7#5.
To hear how the chord sounds simply strum over the soundhole.
You can use UkeMaster in three different orientations. In portrait it shows the chords as in sheet music. In landscape it can show the chords as if you are looking at your own ukulele or as if you are looking at someone else.
Some chords have more than 4 notes in them, but on the ukulele you only have four strings. Therefore some notes are omitted. Mostly the 5th can be omitted without changing the sound very much. Sometimes even the root can be omitted, but especially when there are other instruments around that already play it.