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After finding these instructions I decided to try to construct such a device. After ~$20 at Rat Shack and a couple hours of work I had the above. However, since I run RC5 all the time, watching CPU usage is pretty boring. Stealing some code from Rob Malda of Slashdot fame I hacked out a simple daemon that would make the geektoy act like external modem lights. Now in version 0.5 the code is slightly cleaner and support up to four input lines to be used as switches. My model, which only has one switch currently (used for making and breaking ppp connections) is seen above.

The code is currently set to watch input lines 10, 12, 13 and 14. If you wanted you could add a fifth switch on line 11 (seen as the most significant bit returned from port_in(port+1)) but it is inverted. You could also add four more LEDs on lines 17, 16, 14 and 1, though I suggest leaving line 1 open for power, since certain parallel ports require a pullup source to register input.

Here is a nice tarball of all the code, the docs and two utility programs I found amusing: geektoy-0.5.tar.gz

I have found geektoys make good presents. The latest represents the state-of-the-art in geektoy design, though sadly I have no pictures. Yet.