All mac computers include free parenting security software. For more information see Apple.com
Wireless Internet:
With an airport extreme wireless box, you can set the hours internet access is available. For example, if your child arrives home before you leave work, you can “turn off” internet access until you arrive home. For more information, see Apple.com
Also see OpenDNS for a free filtering service. If you have wireless internet, you can block access to certain sites from any computer or mobile device on your network. (Mobile phones, games, etc.) For example, if someone brings a laptop to your house, you can limit websites/content accessible through your network. (As opposed to software installed on a specific home computer.)
I have been using this free service for over 2 years now – it is excellent.