Hi! I am actually the owner of Kadydid Designs, and those car seat covers that you shared the link for are my own design.
These car seat covers are quite popular. I started making and selling them when I got numberless compliments on the one I used with my last baby. I live in Arizona, so it's obviously not cold, but it was GREAT for keeping people away from my tiny newborn. No germs, no unwanted fingers near the face and no weather elements. There is still plenty of room for air flow since it's only attached at the handle, and the ribbon ties prevent the blanket from slipping anywhere.
You can find similar tutorials for these all over the internet. They're not hard to find. If you would like to make a replica of my cover, I would be happy to sell you just the pattern (in pdf format). You can contact me via my Etsy shop.
Good luck with your new baby!! And thanks for all the exposure this morning!