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Phone out of juice? Just twirl this tube charger

Voltmaker is a prototype dynamo that gives you emergency power with a few minutes of cranking. An attachment turns it into a handy flashlight.

You wouldn't want to spend hours twirling Voltmaker to fully charge it, but a brief spin works in a pinch. Indiegogo

If you're far from the grid and your smartphone battery is running out, you'd better have a backup if there are no other phones around. This recharger gives you power with a flick of the wrist.

Voltmaker is an award-winning, patented design and Indiegogo campaign for a USB charger that can give you emergency power by spinning the dynamo. The 6-inch, 10-ounce device can also be recharged on a standard outlet.

If your phone is dead and you're hiking in the woods, spinning Voltmaker for two minutes will generate enough power for a phone call lasting several minutes, according to the campaign.

Fully charging Voltmaker's 2,000-mAh battery manually, however, would take two to three hours, so the crank is really for emergencies.

Voltmaker can also charge USB gadgets like MP3 players, cameras, and GPS devices.

A flashlight accessory attaches to the tube via USB connector, turning it into a portable light. Two minutes of spinning the dynamo produces about 20 minutes of light.

The French designers behind Voltmaker want to make other attachments such as a radio, fan, and water sterilizer. Meanwhile, they're looking for $200,000 from Indiegogo donors to fund production, with shipping promised this fall.

They're offering Voltmaker for $69 or $89 with the flashlight attachment. Check out their silly promo vid here.