Here's a comprehensive three part review of a wonderful home security system, ideally suited for people who travel and necessarily leave their home vacant/unattended.
The Logitech Alert Home Security System is easily installed, easily configured, and easily used. It provides high quality audio and video recordings of 'events' triggered whenever the cameras detect motion in their field of view. It can send you realtime alerts and pictures of the motion events when they are detected, and allows you to remotely monitor your system from anywhere in the world, on your phone or on your computer.
Affordably priced (list from $300 and less on Amazon) and able to grow to as much as a six camera system, the Logitech Alert seems to represent as one of the best home security systems currently available. Recommended.