Every year, around the Harvard/Yale Game, DAPA distributes these card holders. They have an adhesive back that allows you to slap them on your existing phone case. They are made of a rubber material with just enough stretch to hold 2 cards. The amount of utility that I derive from this simple pouch on my phone is incredible. I do not misplace my ID, because it’s attached to something a lot more valuable. Moreover, I don’t have to go fishing for my ID when its time to swipe into the dining hall. I think add-on products like this one, that play on ubiquitous items (phones) and behaviors (the fact that we always have our phones with us), belong to the ‘quietly ingenious’ category.