Step 1: Purchase Buffalo Airstation WHR-G54S.
Step 2: Flash with dd-wrt.v24_std_generic.bin dated July 16 2007 using TFTP.
Step 3: Perform SD/MMC Card Modification to add some flash storage. Completely ignore section where you determine where the solder points are, and just get soldering. Also ignore the section about SD card adapters and solder your wires directly to the card. All you need is about 30k of storage space for the AutoAP script, so any crappy old card will do.
Step 4: SCP autoap_test_2007-07-16beta.sh to the new /mmc directory on your router, rename autoap_test_2007-07-16beta.sh to autoap.sh, and chmod 755 autoap.sh.
Step 5: Add “/mmc/autoap.sh &” to the startup section in the DD-WRT administration pages.
Step 6: Drive around and see if it works. Look at http://X.Y.Z.1/user/autoap.htm to see what the script is doing.
Here are some scans of my completed board so you can see the solder points a bit better…