I store all my most useful relevant books (or at least pages from them), gear instruction manuals (JIC repairs etc.), pics of wildlife/plantlife I might see, important ID/CC info (password protected), etc. on my iPod. Battery lasts a long time with all the RF stuff turned off, very clear screen (but lousy in sunlight), small, quick to recharge. Does the job.

I don't rely on it, but I do count on it. I like to think I already know beforehand all the stuff I *need* to know. I'm big on planning, not as good at it as big on it lol, so a backup is handy. In college (engineering) we were always taught to never memorize stuff you can easily get from books (they meant formulae/data), rather to use the brain for the stuff that isn't in the book. I'm big on books too lol.