Can I just say that I LOVE scouring blogs/Pinterest for good parenting ideas! So many Moms out there have the best ideas!!
Take this one from Less Than Perfect Life of Bliss for example:
Road Trip Clips!
This lovely lady scrapbooked some clothespins but you could also just buy some different colored clips and coordinate with your child's assigned color (pink for jane, blue for john, etc)
(which is what I'll do as my kids are color coordinated)
You'll have to head on over to her blog in order to see how she fully incorporates them
but in a nut shell... if you fight, whine, or make a bad decision your clip comes down. If your clip comes down you don't get a treat at your next stop.
She used these clips for a 16 hour road trip with much success! However, I see no reason why these couldn't be utilized for a 10 minute car ride to the grocery store!