Watchmac for Mac

From bloo7:

Your Mac can already stop unwanted access out of the box. Sometimes it is desirable, however, to know when someone tries to circumvent these measures. This is where Watchmac comes into play.

Watchmac monitors your Mac for possible infringements. For instance, when someone tries to unlock your screensaver but fails to enter the correct password, Watchmac will record this event and can even take pictures using the built-in (or an externally connected iSight). Best of all, Watchmac can even send you an email alerting you about the infringement.

And remember: Some intruders are even in the family. Even though you probably wouldn't count your children among them, Watchmac is nevertheless a great tool for detecting when your children don't play by the rules.