I found one of these on eBay the other day

http://www.ebay.co.uk/itm/121126647632?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Just connect your PS2 keyboard to it and then you get serial and parallel outputs related to the keys that you press.  I'd thought about building my own interface, which would be pretty simple to do, but this seems like it will do the job.

Less than £3 delivered.  Ordered.

I'll connect it to my Arduino Uno first to see what it sends out.