That is a good idea indeed. I thought about a mini one key usb keyboard that could send the CTRL-ALT-DEL signal, but did not find one yet. You solution is obviously easier.
I want to replace my NSLU2 by a sheevaplug I just acquired. I miss the CTRL-ALT-DEL button from the NSLU2, at the moment I am login through ssh to issue a halt command. I there a way to make this work with a button?