While very cute, this is pretty unsafe. As a RN who has worked with trauma and surgical patients: there should NEVER be anything between the seatbelt and the person, even in a booster seat. In an accident the material compresses and the person flies forward several inches further. I know this doesn't sound like a lot but that can make a big difference in outcomes. It also makes it more likely the kid will slip out of the restraint. I hate to be that person that makes this whiny comment, but this one is actually important. Do not modify restraints.

If you look at the tutorial, this is a pillow with velcro loops on the back to secure it to the carseat straps. The pillow doesn't go under the straps but on top of them, which would be very unsafe. It doesn't seem to me like having the thin, non-compressible velcro loop around the carseat strap would interfere with the safety of the carseat, as long as the straps are properly tight BEFORE the pillow is put on.

With a booster seat there would be an issue because the pillow could twist around between the kid and the seatbelt during travel and then interfere with the auto-tightening feature if there were a sudden stop or accident.

Oops, on re-reading my comment it is unclear: I mean it would be unsafe if the pillow were UNDER the carseat strap but on top seems like a non-issue.

Thanks for a cool tutorial to make our lives a little more bearable on 18 hour car rides to grandma's house.

Attaching anything "after market" to the seat can void its warrantee. Most of the main brands have this in the fine print. There are many genius ideas that just are incompatible with our litigious society.

What if velcro were attached to the strap, and the pillow velcroed atop the strap? Having done road trips with little ones, I can see the value of a pillow for napping.

Thank you for bringing up these important items to keep in mind.