I love those little blue travel routers! (I assume that's what you're talking about) I use them all the time to troubleshoot WiFi issues, or to turn wired-only devices into wireless clients. They're perfect for that. My favorite part is that they can be run off powered USB ports (they use a standard micro USB cable), so sometimes I can power the router off the device I'm trying to connect to the wireless network. Too cool.

My guess is that the power consumption of the OnHub is a mix of the much more elaborate antenna array and the other stuff Google has planned for it, including Zigbee and Brillo, as well as the rumor that it might run Android in the future.