I have that under my car seat but seeing as mine is 6 months, she doesn't produce a lot of mess yet.
Zebug,I use Prince Lionheart seat protectors in all of our cars. I also have clear heavy vinyl protectors for the front seat backs so there not getting scuffed & dirty when the kids kick them. You should be able to pick both up at Babies R Us.
Prince Lionheart - Travel - 0560 - Two-Stage Seatsaver