Here is a wireless security system that lets you attach multiple security cameras to keep an eye on your property. You get 4x 720p HD outdoor night vision wireless cameras to get started. The device has a built-in router and two WiFi antennas, providing you with coverage up to 1000 feet in an open area.
The device supports 3.5″ HDDs up to 4 TB. It lets you view camera footage from your smartphone. Costs $300 at this time.