The first add-in has been made available for Windows Home server codename Vail (or WHS v2).
"Wake On Lan" by AWIECO gives you the ability to turn on a computer remotely. It enables the Home Server to start up every computer attached to your network. The gadget shows a list of all available and connected computers within your network and provides the possibility to start them up from any location inside your network or via internet, by just one mouse click. The gadget automatically recognizes, if a computer is already turned on or if it is booting up.
You can grab the free "Wake On Lan" add-in for Vail from here.