I realize that registering your car's handsfree set to your PS3 has absolutely no practical value. I thought it would be fun to see if I could really register my cars wireless Bluetooth setup with my PS3. Given that the PS3 supports BlueTooth I figured it would but I wanted to see if it actually worked. The back wall of my living room shares a wall with my garage and with Bluetooth having a range of 30 feet or so it wasn't a stretch for it go go the 10 feet or so even if a wall was involved.
All I had to do was turn the electrical on in the car and then have the PS3 search for it. Sure enough it worked to perfection, as both the car and the PS3 recognized the link. Here are some pictures of the XMB interface with the headset registered.