Yeah, there were tons of "basically a GeekPort for PCs" in the industrial control/test and measurement world, but not much aimed at home hackers or even really low-end experimentation. I don't know if that's a result of just the parallel port being used so often and it not being cost-effective, or what.

In the pre-PC home computer world, there were products like that, and even in the early x86 ISA PC world, there were analog/digital I/O cards that didn't break the bank.