I were looking for something like this for a long time now and couldn't find anything so I wrote one myself . It's using device TOS6205, and you can check if you have one by typing:
ioreg -lw0 | grep TOS6205
It's my first driver and event first application for Mac OS, so don't be mad if this brakes anything on your computer:).
Top work for a first effort. This works perfectly on my toshiba nb200 with 10.0 snow leopard. Unfortunately it's not working on 10.6.5 (which I need to make my wifi work!)
Any ideas what's broken it in newer versions?