If you know what each pin is connected to, etc... you could get an analogue capture unit plugged into a usb port and wire the unit up to the ecu pins (prob best make up a loom using male and female ecu connectors).
Then it would be easy enough to write a program to scan the inputs and display the results on screen.

Only thing is - those boards are pretty much the same price (if not more) than simon's monitors anyway, and you have to wait for laptop to startup, shutdown, prob will crash a few times, install it somewhere in the car, etc... I'd call simon me...