The Skinny: The HydroPak replaces batteries and generators with cartridges that can sit on the shelf for ages, activated with water for 12 hours of power. They're quiet with zero emissions, and each $20 dry cartridge cranks out a lot more than any battery can—400 Watts through an AC outlet and two USB ports. The Catch: The device costs $400 and it's still in beta, although that's a lot cheaper than other fuel cell products. But it's a real product, rolling out first next week at CES, and samples will be available in February. [Millennium Cell (pdf)]
only if the benefit of zero emissions from the unit out weighs the emissions cost of MAKING the unit itself
I am no expert, but that won't stop be from pretending. I have had discussions with various 'expert' environmentalists, and it is a safe rule of thumb that the energy used to create a device is about 10% of the energy used to operate it. They primarily were referring to automobiles and electronic gadgetry, but I suspect the rule of thumb will work with this as well.
How much noise does it make?
If it is like other fuel-cell type items, the answer to that is 'none'. It is normally a chemical reaction that does not require any moving parts, save perhaps a fan if heat is a result.