This is the coolest thing I've seen in a while! I would love to have a chalkboard front door so that visitors can leave a message if I'm not home. And if doing the whole door in chalkboard paint isn't possible, hanging a small chalkboard on the door instead is a good idea. I've seen this before on pantry doors, cupboard doors, kitchen and bedroom walls, and even bathrooms and hallways. I myself have a stick-on chalkboard on the inside of my cupboards that I write shopping lists and emergency numbers on. (I'll include a picture of mine at the end here.) I've also learned that you can buy or make chalkboard paint in multiple colors, so your front door does not necessarily have to be black.
Inside my kitchen cupboards (an old picture, I've since gone vegan so my shopping list looks much different)