The Family Time app lets you shut off all WiFi internet access within your house, and restores it when you want.
Has been tested to work with the following routers (in specific configurations - your mileage may vary):
OpenWrt Barrier Breaker (SSH and HTTP)
OpenWrt Chaos Calmer (SSH and HTTP)
Technicolor TG582n (Telnet)
Thomson TG585v7 (Telnet)
Note that if you do not have OpenWrt, you can still install this software and then request that we add support for your particular router. Over time we hope to add support for more types of routers.