There is at least 1 freeware program that creates an encrypted file for you to store such info - I don't remember the name - maybe ePocket or something like that. Anyway - look here
http://www.wm6software.net/ I think that's where I saw it. I haven't decided if I want to put that type of info on my Titan yet. And it could possibly be handy to have that or CC info so you don't have to carry but you'd have to find a very trusting store to only take the number and not have a swipe. But it would be good for ordering online and the like. GL.
Just had a thought - look for keyword wallet or ewallet...