One of the weirder things about cell phones is that you have a huge number of people inexplicably talking to themselves in public. As phones shrink, it becomes less and less apparent that they're using a device to speak to another person, and looks a lot more like a crazy person babbling to themselves. This is strange.
I'm imagining an implanted device, that controls like a phone, but can be operated by thinking. Imagining a number at the phone would make it dial, and imagining talking to it would modulate speech into the connection. So you could "talk," but without talking.
Probably too invasive to actually build, but it would help people with vocal chord paralysis, and allow people to make phone calls without, you know, endlessly talking to themselves in public.
I'd also like to see this applied to computer interfaces, where it could first type from your thoughts. Then cursor from your thoughts. Then replace the monitor with directly injecting to your "mind's eye." And in the end, I compute while walking down the street, with no one the wiser.