At a high level, I took a mirror I had bought cheaply at Target and attached vinyl lettering I designed and made at TechShop San Jose.
Total cost: ~$12
Mirror: $10 (I think)
Black Vinyl from TechShop: $2
Step 1: Design the Checklist
I then used Adobe Illustrator to flesh out the size of the stickers (just a little under half the width of the mirror was what I wanted), to pick out the font I wanted, to design the squares (I used Wingdings and added an outline to thicken the boxes), and to arrange the list visually.
Below is how the design looked digitally: