Technically this should be suitable for use on anyone, not just my buddy Ryan (whose name & face are used because he's good-natured, ABSOLUTELY NOT because he's the only person around here who sometimes needs a shame timer).

In Settings, choose a timer duration; tap the screen to start the timer, and tap again to reset it; if it gets to zero, it plays an angry audio clip (some of which are, uhh, not exactly suitable for children).

If you'd like to fiddle with the source code (adding your own sounds, etc.), it's at: https://github.com/kuhrusty/AllOverButTheRyan