This app was mentioned in 3 comments, with an average of 2.67 upvotes
I quite like Pay Back. I believe it was posted by the dev here a while back but it's still relatively small (1,000-5,000 installs)
It's an app for managing I Owe You's. If you borrow or lend money out to friends a lot for small purchases and tend to forget easily it's great. It has a beautiful Material Design as well.
This is the app you meant, right? Looks good.
Very simple/straight forward. Works perfectly for me.