Line6’s MIDI Mobilizer was the first iOS MIDI interface to hit the market and it’s still a great option for hooking up external hardware to your iOS device.
Plugging into the dock connector, the Mobilizer provides MIDI In and Out connections via 2.5mm mini-jack sockets, with cables converting the signal to the standard 5-pin DIN connection.
The downside is that Line6 originally used a proprietary SDK (Software Development Kit), which means that the version 1 Mobilizer is only compatible with a relatively small number of apps.
The newer MIDI Mobilizer II supports CoreMIDI, making it much more widely compatible and a good alternative to the Camera Connection Kit for iPhone and iPod Touch users.
Find out more about Line6 MIDI Mobilizer II