I agree with most of your points but I'd like to add that people seem to prefer one broadly capable device because of the nuisances attached to having multiple devices. If every piece of clothing came with invisible sensors that monitored our vitals and communicated them to, perhaps, a single hand-held device that we carry with us, I'm sure people wouldn't mind.

As things get smaller and smaller, it's less about what you're carrying as it is about the functionality provided. Think Web 2.0. Fifteen years ago, something like GMail wouldn't make sense because Internet speeds and browsers were not advanced enough to handle such features, therefore people wouldn't even think to demand them.

Think Virtualization. Even 10 years ago, laptops were too slow to handle a whole lot. Now I've replaced two desktops and a laptop with a single MacBook Pro laptop (Dual Core 2.4ghz, 4GB RAM, 320GB HD) and VMWare running Ubuntu and Windows XP. I'm no longer thinking hardware, but instead thinking about what I can do with all that power in one spot.

If the technology existed to put podcasts on earrings and listen to them clearly, then I'm sure the technology would exist to wirelessly sync all your earrings so they all contain the same podcasts.