While researching Monroe Nivomat shocks I found this description of how these shocks work on the AG Sachs website:

The technology:
The Nivomat is installed on the rear axle in place of a conventional damper. Fully automatically and without additional electronic systems, this compact device pumps the vehicle up to its optimum ride height after only a few meters. The Nivomat takes the energy needed to do so from the relative movements of the wheel and vehicle body. For every load condition, this maintenance-free system sets the ideal vehicle height, thus ensuring a safe and comfortable drive. An electro-hydraulic auxiliary system allows the Nivomat to operate either via a manual switch or in automatic mode including when the vehicle is standing still.

This from their product brochure.

Quantcast has an interesting online live stats graph available.  This graph shows the caddyinfo.com homepage and the forum site: