I have a lapdock for my Bionic. It not only needs the app, but needs to connect the USB and hdmi ports simultaneously. The Xoom doesn't fit on the dock on the lapdock. Just use the standard dock and a Bluetooth keyboard. Or buy a Bionic and a lapdock. They're totally different.
The biggest benefit of the lapdock, in my opinion, is it gives the phone a big screen. The XOOM already has a big screen.