I bought my son an inexpensive 2002 Audi Quattro for hopping between locations while he goes through Apprentice University. We do get occasional ice storms, so this seemed like a good idea. I also have a couple VW TDIs, so I already have the Ross-Tech VCDS that can work with the ECU and other electronics in this car.
When we bought the car it came with only one key, and I quickly found out that the VCDS would help me to program remotes, but it wouldn't help me with the RFIDs in the immobilizers. I didn't want to spend an arm or a leg on keys for a cheap car, so I hunted for another option. I found that I could get a couple simple metal keys cut for cheap, but there had to be a way around the immobilizer.
Well, I realized that if the RFID was kept at the ignition switch, it would always be visible and any properly-shaped key could start the car. So, I built this to hold the RFID in place.
Yes, this compromises the car's security, but I've had much more valuable things in my life protected by less-secure physical keys and locks that could be picked more easily than this Audi's.
After doing this, I've actually printed a key from Jason555's Audi Key model https://www.thingiverse.com/thing:1844427 and actually used it to start the car!