This app helps you count things. Just tap the number to make it go up. Supports counting by 2s, 3s, etc.; counting many things at once; counting up or down; sounds, so that you know you clicked without looking; named counters and multiple colors so you can see which counter you're using at a glance. I initially created this to help my wife keep track of where she was in her knitting patterns, but of course you can use it to count or tally whatever you like: stitches, students, pattern repeats, laps, drinks, how many times you've gone to the gym or what have you.
If you want this app but don't want to pay for it there is a free version available which has ads at the bottom of the screen.