Here’s the basic idea. With Arduino, it’s really easy to connect boatloads of cheap sensors. Using this setup, that boatload of cheap sensors can now be on the internets. They can email you when things get too hot, too cold, too smokie, too gassy, or too bright. And your dog can email you by barking! You can also view the status of sensors on your smart phone. These sensor nodes are wireless, so you’re not constrained by the location of ethernet ports.