Home Defense, Geek Style?

Yo Maing writes "So my mom got lives alone, and got her car broken into last night. We have a motion sensor light in the driveway, and the car has an alarm but apparently both of these deterrents were ineffective. Crime has been rising around her neighborhood, and only action the police can take is to file a report. So I ask you, Geeks of Slashdot, what tricks do you guys have to defend yours and your loved ones homes against crimes like this? Not looking for anything that would get someone injured, but more in the area of detection and repulsion. Anyone have a holographic Yeti generator to scare away intruders? :)"