Well, with this app you can disable internet connection for a device on the same network. So if someone (anyone) is abusing the internet wasting precious bandwidth for a Justin Bieber videoclips you could just kill their connection and stay happy with a full bandwidth just for yourself.
After a long long delay, I present to you brand new WiFiKill.
This is an early release so be gentle. New features will come after this code proves to be stable.