Am I they only one who thinks this could be done with a microcontroller and relay? I doubt that the one you looked at would be suitable as it doesn't give a direct digital output, instead the reader is integrated into a phone, somehow. The Credit card ones at the supermarket (they also have keypads which would also be cool) would be a better choice. All you need is a microcontroller to recognize the digital output (it's probably in R232 serial) and then if it matches a number stored in the EEPROM of the microcontroller activate a relay that connects the ATX power switch for a second. Your could program it by swiping a card and seeing what output you got, then setting that one to memory, (meaning you could use your license). The downside is that this is not very secure and any idiot could still turn on the computer by crossing the ATX control wires together. The reader would be purely for show.