Taken From: http://www.popsci.com/popsci/how2/article/0,20967,1076525,00.html
Be Your Own Hotspot
Turn a backpack into a portable, solar-powered Wi-Fi hotspot, and share a high-speed connection anywhere
By Mike Outmesguine
I love the fact that more and more devices are sporting built-in Wi-Fi�the Sony PSP, smartphones, even Kodak�s EasyShare-One digital camera. The lone hitch: Wi-Fi is useless without a hotspot. Sure, thousands of spots are available, but few are free, and coverage is far from ubiquitous. What if you could marry the short-range power of Wi-Fi with the huge coverage areas of high-speed cellular services such as EV-DO to create a portable hotspot? You could use any Wi-Fi-enabled gadget anywhere you�ve got a cell signal. Play multiplayer games with friends in the park, or blog an event in real-time. Since EV-DO works at freeway speeds, you could even give Internet access to an entire road-trip caravan.
Those are exactly the kinds of things you can do with the backpack below. Its secret ingredient: the Junxion Box. Plug a cellular-network card into the book-size open-source-based device, and voil�instant Wi-Fi hotspot, with speeds averaging around 700 kilobits per second. To power the box, I wired it to a 1.2-amp-hour battery and dropped both into the Voltaic Systems backpack, which has a built-in solar charger. Now I can surf for as long as three hours without being tethered to anything but a cell signal. The project isn�t cheap, but prices for the components and service are sure to come down in the next year or so. In the meantime, you can find me in the hills around Southern California. I�ll be the one surrounded by PSP-packing hikers.
See more photos of the backpack here.
These parts are available at any electronics store:
Credit: Illustration by Mckibillo.com
2) To build the power-adapter cable, cut a length of red wire and a length of black. Strip one end of each wire and crimp a spade terminal connector onto each.
Strip the other end of the red wire, and solder it to one end of the fuse holder. Wrap the connection in electrical tape. Take apart the male DC power plug. Solder the end of the black wire to the negative terminal of the plug and the red wire to the positive. Wrap the exposed positive connection in electrical tape, and reassemble the power plug. Install a 20-amp fuse.
3) Connect the Junxion Box cigarette-lighter adapter to the backpack �power out� plug.
4) Connect the battery cable to the �battery� plug on the backpack�s charge controller.5) Take a hike!