iOS: If you need to get a quick head count of a room, or you're tracking anything else with numbers, you'll find plenty of counter apps in the iTunes App Store. However, most require you to actually look at the screen when you're counting. Tally uses a simple interface to let you tap anywhere on the screen.
Tallying up numbers and scores usually requires you to be looking up at the world, not down at the screen. Tally makes this easy by turning your entire screen into a button. Every time you tap the screen, the number goes up. If you're tracking something like scores, you can set the steps to any amount you like and have multiple tallies running at once.
Tally (99¢) [iTunes App Store]