A polished knife blade can/may work in a pinch....you're talking more about overcomming/adapting a shortcomming rather than planning for an emergency though. People have used cd's and the little hologram on bank cards before with sucess, but again it was crap hits fan, what do I have that I can use vs. IF the crap hits the fan, I have brought along this for just such a purpose.
Not trying to discourage you in the least, it is excellent that you have thought it thru and come up with a "chips are down" solution.
And if you guys bring a portable cd player and some cd's now you know you can use that too

-Bill Liptak