Integrating Technology Into a Long Trip?

xsalmon asks: "I am about to undergo a long trip around the continental United States, via hiking/cycling/walking and other self-propelled means of transportation, to raise money toward AIDS/HIV research. What kind of utilities/devices would you bring to increase safety/security? I'll be hauling enough in my backpack as-is, so any suggestions would have to be lightweight and portable enough. Any ideas?"