Wikipedia describes Sideshow as:
a new technology that lets Windows Vista drive auxiliary, small displays of various form-factors where ready-access to bite-size bits of information could be imagined. These include displays embedded on the outside of a laptop lid or on a detachable device, enabling access to information and media even when the main system is in a standby mode. Data can also be displayed on cell phones and other network-connected devices via Bluetooth and other connectivity options.
I will be watching this feature to see what comes of it.