Ask Slashdot: Linux-Based Home Security

Grady Martin writes: I got a new job. Everything about it is perfect, except for one thing: The overwhelming majority of affordable housing within driving distance lies in an area known for its high crime rate. A home security system would afford some peace of mind, and a system whose code I could tinker with would afford even more. What Linux-based options are available? What experience do you have with such systems?