This is a relevant topic to me today. I am in Jakarta right now on business and missed the earthquake in Japan by about 15 hours as I passed through the Narita airport. Anyway I have missed 2 other earthquakes in Jakarta in the last few year by about a day. So when I am traveling, I have my "best I can board a plane with" gear in my small frameless REI pack that I have an extra large external pocket sewed on. For the carry-on, that includes a ziplock of M&M Peanuts, some almonds, water bought at the airport, Jerky of some kind, and then basic survival items including space blanket, stuffable (1/2 fist sized stuffed) nylon duffel, meds and survival kit which includes water purification tabs, metal cup, small compass, small led (both on a key holder in my belt Molle). A large organge bandana, spare T-shirt, pair set of undies and socks, soap and toothbrush. Oh yeah, and extra recharge for the IPhone.
When I arrive and get to a room, I pack into the small REI my airforce survival knife and a Mora and I strap on my Leatherman wave. In the hotel room I make sure I have at least 1 gallon of bottled water + I always keep the sink and bathtub filled with water. I also include in my luggage (not for the pack) another pouch (one made for first aid gear by Early Winters back in the 80's). That contains some additional first aid, tools and gear including some dental instruments, tie downs, silver dollars, knife sharpening, hook and line, and several types of fire starting gear.Once in country I always have on my person a Tool Logic Knife and the Leatherman and a significant amount of cash (US$ and some of the country money depending on the country) and obviously my passport.
The Pack is ready to pick up and run with at a moment's notice. The luggage is ready to go whenever as well but if need be I can easily live without it. My Iphone has "Where There is no Doctor" and "Where There is no Dentist" downloaded in .pdf format along with other essential and nice to have files. The same files are on my laptop. There's more prep stuff but that is the highlight. Since I am on the road more than 100 days per year domestically and internationally this stuff is always with me.