Look on the bright side. In the case of a commercial airline crash, you will probably only have to survive for minutes or hours (if you survive at all). Most crashes occur at takeoffs and landings, and the location of the plane in flight is known quite accurately. If by some chance, help does not arrive immediately, you will be able to search through the checked baggage for survival items.

Three years ago an Alaska Airlines flight crashed into the Santa Barbara Channel just off of Anacapa Island. A boat arrived on scene within fifteen minutes (no survivors).

Probably the items most useful after a crash would be first aid knowledge and equipment - the ability to stop bleeding and stabilize fractures should be paramount. Help will arrive soon.

I share your feelings - I am not fully dressed until I have strapped on my Leatherman. I am less than thrilled at placing mine in checked luggage, but planes have been hijacked with less.