What I use in the car is also from Petco, but I believe it's different then the item you are referring to. It's just a small strap that has a seatbelt latch on one end, and a leash hook on the other. I just use a regular harness I already had on him, and just attach it to that....I leave it in the car all the time. It works great!

As for the halti, I've been walking Nebo on it for quite a while now. It works amazing for the pulling. He still hates it though...sounds just like Ruby...he'll walk for a while then stop and paw at it. I give him treats while wearing it, and tell him "uh-uh" and stop and make him sit when he paws at it....he still does it though. I don't know if he'll ever enjoy it.