NeTV enables overlaying your web content on existing HDMI video feeds, such as those from a BluRay player or cable box.
Inside, it's an Angstrom linux box running Webkit that features chroma-key video compositing. Out of the box, the reference firmware enables the overlay of Facebook and Twitter feeds, and SMSes from Android phones. The UI is written in Javascript/HTML, making it easy and fast to develop your custom application.
The system also features a convenient HTTP API which uses POST commands to issue events to the screen and control device behavior.