This could initially be marketed for quadriplegics, but I think it would catch on for the non-disabled masses. All this stuff is already baked, but someone needs to put it all together and show some love for the quadriplegics who want to surf the net.
Although Windows, for obvious and quite under$tandable
reasons will not allow booting from a USB drive, Linux has been able to install itself and boot from a USB flash drive for some time now. I can carry my little flash drive to any computer, boot from it, and it is essentially my computer - my programs, my files, my settings, everything. My little Mercury modem can access 3G signal to bring me internet over the cell phone network. It even has a slot for a micro SD card, although for driver reasons I cannot install a Linux distro to the micro SD and boot from it... although I really wish I could. Technology exists to monitor eye movement, and there's Dragon: Naturally Speaking for voice-to-text.
If all these were put together into one stick it would be perfect for quadriplegics. The stick would be too big so it would cover adjacent USB slots, but you wouldn't want it on the back of a computer anyway for reasons I'll cover shortly - it would have a USB extension cord. It would have some onboard memory, say 32 or 64 gigabytes (which isn't a whole lot, but we're not trying to store our whole video library here - that's what 10 terabyte external hard drives are for. 32 gig is plenty for an OS, programs, music, etc.) On boot it would talk to the computer's BIOS as a normal flash drive.
On the end with the USB port it would have a slot for a SIM card, and it would function as a wireless/3G/4G modem. On the other end of the stick it would have a small camera and microphone. The stick would be positioned right above the computer screen, with the cord connecting it to the computer's USB port. Maybe put a small clip on it so it could clip onto flatscreens/laptop screens. The camera would zero in on the user's eye movements and, with a short calibration sequence right after boot (look at exact center of screen and blink once) it could link the cursor to eye movements. Blink once to select, twice to open (double click) three times for right click. Dragon would handle generating typed text - unless the open source community has come up with a freeware alternative by that time, which they are probably working on now.
Why eye movements? Because some quads don't have neck muscle control.
With this simple stick, no matter where a quadriplegic was he could borrow anyone's computer and boot to his own computer system, get online, use mouse and type, talk to someone on voice chat, hang out in an IRC chatroom, watch a youtube video, anything normal people can do online.
What? A USB port couldn't provide enough power to run all that on one stick? Actually it could, but a USB cord with a second short cord for extra power is thoroughly baked - one came with my external USB powered DVD burner. The cable that connects the Quadriplegic Computer Stick (QCS) to the computer could have a spare power-only cord attached.