...the waste water with dissolved metals will be far worse than the air pollution from burning oil. It doesn't appear that's the case. I get the impression that the fuel cell is a closed-circuit technology. The water produced is the byproduct of burning hydrogen, which produces pure water and there is no contamination. I remember doing an experiment like this in my high school chemistry class. We put a spark in a test tube that we filled with hydrogen as a result of electrolysis. The spark ignited the hydrogen, which sounded almost like a dog's bark when it exploded. All that was left was a little water vapor in the test tube.
Yes, but where does the energy to separate the hydrogen & water come from? I am guessing from the discussion of batteries, that is the source of energy.
Another path they might be using is to make hydrogen by reacting water directly with an active metal. The energy source in this case is the metal, you are recovering a portion of the energy used to refine the metal. For example, you can make hydrogen with freshly powdered aluminum and water. It's been done (but with aluminum wire, not powder)
http://www.keelynet.com/energy/cornish.htm In this case you wind up with aluminum hydroxide as a by-product.