http://www.southernstars.com/products/skywire/index.html
I've gotten as far as opening an input and output stream with it, but I haven't had time to dig up an RS-232 device to try talking back and forth.
What I'm not sure of is what sorts of apps they'll let into the app store that repurpose the cable.
EDIT: Here's my test code thus far:
https://github.com/frankus/SkyWireTest
Hell, GNUStep was created just to port a single application!
http://www.southernstars.com/products/skywire/index.html
I've gotten as far as opening an input and output stream with it, but I haven't had time to dig up an RS-232 device to try talking back and forth.