There exists assistive technology devices that use tracking of a reflective dot by infrared to control a computer. They cost in vacinity on USD $4-500.
Now take a look at this video and think about the unforseen possibilities of general purpose ‘stuff’. And what happens with mass market uptake and the effect it has on lowering costs and barriers to access.
[wp_youtube]0awjPUkBXOU[/wp_youtube]
Hat tip: Lucy Chilli
life tools 
How about that!
Only just noticed that Dave and Lucy were onto this a full month before the rest of the world caught on.
Typical đŸ˜‰
Fang