Mike Outmesguine…Popular Science How 2.0 article on turning yourself into a walking hotspot by using a mobile power source and a cellular-to-Wi-Fi gateway. The Voltaic Systems backpack makes a great platform to build from due to all of the internal wiring and myriad power adapters included in the kit. And I like the Junxion Box as a simple, clean appliance to handle the Wi-Fi to Cellular interface. Link.
HOW TO make a portable Wi-Fi Hot Spot