Grid Connect, an established player in the industrial sensor market, also offers the ConnectSense home security system, which works with your home Wi-Fi router and ConnectSense-branded motion, light, temperature, humidity, water, door and window sensors to monitor the security status of your home. No hub is required. Some sensors use batteries, so they are ideal for placement in areas such as a basement, where you might need a water sensor but have no outlets nearby.
The sensors communicate using Wi-Fi, which may be easier to connect but requires more power than the protocols commonly used by other home automation systems. ConnectSense can deliver alerts by voice call, text, email or tweet. Both the mobile app and the cloud service on which it relies are free. The wireless security system is sold for $149.99 direct (Check Amazon price).