It starts with the phone, the iPod, the watch, the point-and-shoot camera, the Flip video camera, the GPS unit, the compass, the pocket LED flashlight, the universal remote, an entire drawer full of city maps, the deluxe HP scientific calculator that I've had since grad school, the wireless communications unit for my laptop, the pedometer, the metronome, the tuner, and the pitchpipe. To say nothing of the pocket paper notebook.
Now, thanks to the Kindle app, my library is shrinking.
My portable audio recorder's days are numbered. (The stumbling block: when you're recording audio you really want to be able to do it for an hour or two at a time, without stopping for anything, so you don't really want to do it with your smartphone. What if you have to take a call, or tune an instrument, or do a calcuation on your H-P calculator simulator in the middle of recording? But these things are getting so cheap that soon I'll just be able to buy a dedicated one for audio recording. Or maybe it'll just multitask well enough to record audio in the background, with the mics attached by a cord.)
The cost of the smartphone is still too high, and the durability too low, for it to quite replace every single one of my paper field guides for birds and animals -- you want to be able to use the thing in the rain, while standing in the mud, with one hand, without flinching -- but that's almost there too.