Using iPod Touch as Sequencer for Moog?

I have an iPod Touch and a Voyager and I would love to be able to make the two get along…does anyone know if an iPod-to-MIDI cable exists so that I could run a step sequencer app from the Touch to control my Voyager at live gigs? I currently use my laptop for this, but I’m always down for making my gear load a little bit lighter.