Remote Preview is a JavaScript-based tool for previewing a web page on multiple devices, built by Viljami Salminen @viljamis for the Helsinki Device Lab. Just enter a URL, hit Enter, and the new URL gets automatically loaded on each device. Works on platforms like Android, Blackberry, iOS, Maemo, Meego, Symbian, Windows Phone and WebOS. I don't think the GameBoy pictured is supported. ;)

Source code is available on Github.