It is fascinating (and perhaps a bit scary) anticipating the human-technology interface in the next hundred years or so based on the acceptance of mobile computers in recent years.
Based on current trends it is easy to see micro headphones advances for hearing feedback from your personal tech. Other advances are obviously going to be in speech input and control.
One possibility that occurred to me is for a tongue keyboard for discreetly communicating with/thru your personal tech. This is not a clumsy analog keyboard but more like a device that uses 3-d Wacom tablet-type feedback. It tracks tongue movements within the mouth without much hardware - maybe just a chip in the tongue tip possibly plus a thin insert behind the top lip.
This would allow text input by touching teeth and locations like the roof of the mouth, etc. Additional possibilities are opened up with tongue gestures, etc.
The texting would Bluetooth (future equivalent) to cellphone equivalent. Possible words per minutes by an experienced user maybe just a little slower than single finger typing?
College students discreetly discussing a lecture... Special forces silently making plans. All looks like telepathy...
The shortcut for making the ‘lol’ symbol? Tongue in cheek...
Is a tongue input device practical?