Bingo Buddy keeps track of your paper bingo cards. Take a photo of your sheet (or type a card in), check the numbers it read, then tap or type each number as it's called. Every card shows how close it is to a bingo, so you don't miss one.
Your cards stay on your iPhone. There's no account to make, no ads, and the app works without a connection. Bingo Buddy is free, and it's made for 75-ball bingo.