Best Buy was the first retailer to begin selling the "green" portable fuel cell for smart phones and PDAs. Now T-Mobile has bought-in to Medis Technologies' greenwash campaign by beginning to sell the environmental train-wreck that is the Xtreme Portable Power Solution.

Cell-phone manufacturers are doing all kinds of things to both make their products a little greener and to make their products appear greener. Now, cellphone accessory manufacturers are trying to get in the game as Medis Technologies Ltd. has begun selling the world’s first personal, portable, fuel cell power system designed for smart phones.

Medis claims that the $40 unit delivers "20 watt-hours of power to charge a phone multiple times or an advanced flashlight for up to 100 hours before the energy is consumed."

Fuel cells work by producing electricity through a chemical reaction arising from the combination of a fuel (hydrogen, for instance) with oxygen. And while fuel cells show some promise for larger applications, it is not entirely clear whether smaller units like these are any "greener" than regular batteries.

Medis CEO Jose Mejia claims that the electricity produced by the fuel cell "is generated without emitting elements harmful to the environment, such as carbon or carbon dioxide, and without any heavy metals." The company also says the Xtreme products are easily recyclable (meaning you can mail the unit back once it is spent), but the real question is, how often will this actually happen?

"Fresh green electricity can be made available when and where you need it – under any climatic conditions," says Mejia, who added that the gadget is "probably the greenest energy source on Planet Earth."

But the "green-ness" of the new portable fuel cell is being challenged by some who claim it's no better (or even worse) than keeping an extra battery for your cell phone.

"The device not only contains lots more heavy metals than lithium batteries, this device is huge!" writes one commenter at Inhabitat. The fuel cell, the commenter says, is "About 10 to 20 times the size of a typical cell phone battery with a huge amount of plastic and other materials with half lives of thousands of years as well. Green? Not yet."

No, not yet.