I really mean the keyfob combined with a model S.
The Model 3 wouldn’t need this as I guess you’d just carry your phone with you. Although unlocking with implant is cool, if there’s an easier way that’s preferable.
The Tesla backup card is intended as a backup or to give to people temporarily if you want to borrow them your car. However, the “intended experience” is to actually use the paired phone “passively” and walk up to the car.