Looking like a typical guitar effects pedal, iRig Stomp is actually a guitar interface that will work with iOS devices, and is compatible with most iOS signal-processing apps.
We check out iShotgun, a miniature interference-tube or 'rifle' mic, the newest member of the i-Series line-up of cost-effective electret mics designed for use with iOS devices and other portable recorders and cameras.
The iPolysix app faithfully recreates the original synth's architecture, which had six VCOs, one for each of its six voices. Does it do the original justice?
Samplr is a modestly-named app for sample and loop manipulation, notable for making superb use of the iPad's multi-touch surface to stretch, transpose, play and twist up to six samples.
iTrack Solo is Focusrite's first audio interface designed for use with iOS devices, although it can also be used with a computer via its USB 2 connection.
The iO Dock from Alesis is designed specifically with the iPad in mind and offers a pair of 'combi'-style audio inputs, MIDI DIN and MIDI USB plus a handy footswitch socket.