I did purchase one of the doggie seat belts. Stomper HATED it to the extreme. He would bark and scratch at me. I put him in the back seat with the seat belt and he wiggled himself out of it. Little snot!
Since they (the lady across the street gave me this idea) I have a short leash connected to the baby belt on the back window. He has movement to see out the windows but can't come bug me! He doesn't love it and still barks at times but he is adjusting to that much more than the seat belt. Probably not as safe but...
Sometimes I do let him sit on my lap. However, he is starting to get too big!