I'm forced to ask why you'd ever want to connect your iDevice to an old-school printer, but Redpark is making the case that people want apps with some retro chic. So the iOS Serial Cable was born.
Except is doesn't yet have iOS support. Bummer. But Redpark is pushing for Apple to allow developers to create apps for it. If and when that happens, tinkerers and educators could write apps that run with the older hardware.