This is a relatively new app that allows you to connect other apps (or “channels”) using a simple programming logic. It is all controlled by your iPhone. For example, you can use it to connect WeMo devices, which are wifi-enabled power switches you can set up in your home.
You can also connect various online services like Facebook, Twitter, email, weather, Google, etc. and set up trigger actions.
For what looks like a more generic, less user-friendly option, there is also Cosm – the new “Internet of Things”. This allows connections to Arduino, an easy-to-program sensing device that connects to a network.