Native Extensions enable Silverlight developers to access some really cool features of Windows 7 from their Silverlight applications with a set of native runtime libraries, paired with a set of Silverlight libraries
Ø Take advantage of sensors like accelerometers, light sensors, compasses, GPS etc.
Ø Access content from connected portable devices like music players and digital cameras.
Ø Capture and create video from webcams and screen output
Ø Use speech recognition and text to speech capabilities.
Ø Integrate with the Windows 7 taskbar (Jump Lists, Icon Overlays, Taskbar Progress etc.)
Ø And more…