Karl,
If you intend to do this youself:
How much microcontroller experience do you have?
For the doors and windows, consider using magnetic reed switches magnetic reed switches.
You can connect a smoke detector, motion detector, cameras, etc to the microcontroller.
However, you may spend more money developing your own system than just buying one.
A quick google search "wireless security system" found this site: http://www.homesecuritystore.com/c-73-wireless-alarm-systems.aspx
Let us know which way you want to go.
Cabe
http://twitter.com/Cabe_e14
