"The typical American will have at least a dozen computers on his body, in the form of credit cards, rings and brooches. They'll be networked, and they'll get us through security checkpoints, monitor our vital signs, and provide GPS-style directions."
As for getting us through security check points, since Kurzweil did not predict that terrorists would bring down the World Trade Center in 2001, he also did not predict that the main bottleneck in getting people through checkpoints would not be credentialing but having people take off their shoes and carefully inspecting them for...something or other. And checking for bombs in their shampoo.
Devices for monitoring vital signs just did not happen, far as I know.
As for the rest of the computers on our body, it seems people prefer to have one broadly capable device for information, computation, entertainment, and communication, which is the cellphone (with iPhone best exemplifying the ideal of a single device with a broad range of capabilities). Having to compare and buy lots of little communication doodads worn on different parts of the body would just be an irritant (damn, wore the wrong earrings today, the podcast i wanted to listen to was on the other set and don't feel like waiting for it download again...)
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.
As for getting us through security check points, since Kurzweil did not predict that terrorists would bring down the World Trade Center in 2001, he also did not predict that the main bottleneck in getting people through checkpoints would not be credentialing but having people take off their shoes and carefully inspecting them for...something or other. And checking for bombs in their shampoo.
Devices for monitoring vital signs just did not happen, far as I know.
As for the rest of the computers on our body, it seems people prefer to have one broadly capable device for information, computation, entertainment, and communication, which is the cellphone (with iPhone best exemplifying the ideal of a single device with a broad range of capabilities). Having to compare and buy lots of little communication doodads worn on different parts of the body would just be an irritant (damn, wore the wrong earrings today, the podcast i wanted to listen to was on the other set and don't feel like waiting for it download again...)