My husband and I both have rear seat covers in our vehicles, and seat belt restraints for them. My favorite restraint actually clicks into the seat belt buckle (or whatever it's called) on one end, and onto their collar on the other. The other restraint we have hooks around the seat belt after you buckle it then onto their collar. I think I found both of those at Petsmart.
Lesley, Mom to:
~Cash - male, mahogany fawn, floppy, 11/10/08
~June - female, sealed reverse brindle, floppy, 11/5/09
~cat - Dinah **RIP Jinx 3/02 - 9/10**