Buying Windows SideShow-compatible devices today
Interested in owning the world's first Windows SideShow-enabled notebook? You can purchase the ASUS W5Fe directly from ASUS through Windows Marketplace (https://www.windowsmarketplace.com/content.aspx?ctId=397&tabid=1)! You may also be able to find it through your local retailer, depending on your geography. I've been carrying one around for the past couple months, and I must say it's a nice machine (that's an honest opinion!). I do get a lot of questions from people curious about the secondary display :)
If a digital photo frame is what you're looking for, the Momento 70 and Momento 100 frames from i-mate are now available in the US (and have been available in Europe for a while)! Once you get it all configured on your network, just double click on the device in Network Explorer to launch the Windows SideShow driver installation process. The driver is available on Windows Update, so the install should be seamless.
Stay tuned for updates as more devices supporting Windows SideShow come to the market.