I seen another page for a similar project a while ago, but for the life of me I can't remember the address. Basically the guy came up with a mobile pacakge that consisted of an old laptop, a cell card, a router and a few other bits that he could use for a mobile WLAN anywhere he goes. He found it handy to leave in the car and then use another laptop he could use to access it from a restaurant or other nearby location. The whole pacake fit neatly into a briefcase-sized enclosure and only required 12v to run.
I wouldn't want the cell-phone bill if you left the access wide-open though... :roll: