Undercarriage spray wash

I've see the devices for sale that connect to a pressure washer that you roll under the car.
Has anyone tried one?
http://www.tylertool.com/karcher-2-6...kXoaAi_f8P8HAQ
While I don't drive mine in the snow / salt I do live about 2 miles off the hard road and will pick up dirt or mud at times.
Cleaning the wheel wells is no big issue but anything that is on the underside is tougher to reach.
Thanks !


