This is one gift I wish I received. It's the impossibly simple Kids Growstick - a folding yardstick you can use to measure your kid's vertical milestones.
Instead of making marks on the doorframe, you can mount the Growstick and note your child's height there. The benefit is you can take it with you when you move. It's a great way to memorialize your child's growth. You can buy it here for €15.95.