A wish that I had for some time now is fulfilled, I have been able
to add Digital and Analogue Input/Output to the Asus wl500g!
This is done with the K8055 Experimental USB board from Velleman (a board which can be bought as a kit or completely built and tested).
Please find attached the compiled version of the program Cueib (thanks to my colleaugue Stefan who managed to compile it) to control the board (see also: http://linuxk8055.free.fr/). Copy the binary to your wl500g and call it with ./cueib --help to see the opions.