Flutterby™! : Kosher Switch

Kosher Switch® very carefully sets up a mode with random failures so that observant Jews don't have to find a goy to flip light switches on the Sabbath:

Uncertainty through two random failure probabilities. In each of the switch’s cycles, there are two chances that things will fail and that the attached fixture will stay unaffected. This creates two safeiks (Halachic uncertainty): the first, whether or not the light pulse of the Light Pulse Pair will fail; the second, whether the switch will fail in triggering the circuit based on the results of the Light Pulse Pair. There is no way of predetermining how many cycles would be required to overcome for both of these safeiks.

Fascinating application for intentionally flakey hardware.