If you are a Comcast cable TV subscriber and also own an iPad, iPhone, or iPod Touch, you can use them to remotely control your TV with a free app provided by Comcast. After you install the Xfinity remote app to the the device you need to log in to it with your Comcast ID, which is already configured for the TVs and set top boxes in your home, and you can configure each to control them from your device.
In the screen shot to the left you see the Xfinity remote app running on my iPad. The current TV listings display along the middle of the screen, which you tap to see more details about the show. On the show details pane there is a Watch On TV button, which you tap to change the TV to that channel. The communication from the iPad to the set top box is via WiFi and the Internet and the set top and TV must be turned on in order for it to work. Because the remote app doesn’t require line of site, you can change channels for TVs that are on in other rooms in your house. (Let the hijinx commence!)
On Demand listings are available, but right now you cannot select On Demand items for viewing on a TV. Future versions of the app promise to be able to control On Demand as well as provide video streaming, which is already available to desktops for Comcast subscribers.