The Incredible Head is a showerhead that promises "invigorating shower force," even with low pressure. It's also advertised as good for "Navy showers." (More on those in a minute.)
I bought an Incredible Head yesterday ($4.99), and it's a hit with showerers of all ages. It produces tremendous water pressure, so much so that it's necessary to turn the water way down from its usual setting. The Head has a button that shuts the water down a trickle — a good way to save even more water while shampooing. The manufacturer's claim that the Head can reduce water and energy costs by as much as 70% seems pretty plausible.
About Navy showers: turning off the water while showering is, as I guessed, the idea. Strangely enough, Lifehacker has a feature on this very topic today:
Conserve water and save money with the Navy shower (Lifehacker)