I think that's where tablets and ipods and smartphones are going to be for the next few years, at least; a consolidation of all the little gadgets and doohickeys (phone, calculator, camera, music player, portable game machine, pager, password vault, video player, wristwatch, GPS, portable storage, map, notebook, wallet, keys, ID...) you used to have to carry around separately.
That's why Apple's stuff is all aggressively single-tasking; their base assumption is that the device is a swiss army knife of gadgets, and like a swiss army knife it's only good for one thing at a time, and it only has to be ok at any given thing as long as it does everything passably.
We're really feeling this in the game industry, because the iphone seems to be gutting the handheld console market. Why carry around a 3DS or a PSP when you've already got your iphone?
One of the places I think free software has an opportunity in this space is with more technical stuff; if a tablet plus a small arduino dongle could give you (say) a credible portable high-res oscilloscope, for instance, there's a set of people who would find that invaluable. Or something you could hook up to weather monitoring hardware. Or other arbitrary "unsanctioned" devices.