AFAIK, wl500gPv1 has no free gpio pins... Some earlier versions (deluxe?) do had some... Also, some earlier devices had lpt port, which is generally speaking is also an array of gpio pins...

So, for wl500gP you have to connect something to either usb, or rs232, or ethernet. I guess, definitely you need to use microcontroller (mc). From the point of view of mc handling, I'd put these three options in such order: rs232 (simplest) - usb - ethernet (the most complicated).

Example of usage of rs232 you can find in the mc datasheets; I'd suggest to consider lcd2usb project as possible example for usb connection; and ISA-Ctrl AVR-Webserver an example of embedded web server.