Thanks for the suggestion TsVk! - you got me going ! I spent an hour this morning running around, largely on Google, to come up with some interesting information. The leading commercial comppany in this field appears to be a firm called Tobii, originally, I think German, but with offices world wide.
They produce a very nifty gadget, which looks not unlike a slightly reduced Konect bar or a Wii sensor bar that sits on top of your laptop or at the bottom of your display. I have no information about the software employed - they supply that - but they claim it is easy to set up and calibrate the equipment. And so it should be, the asking price in the UK for the basic unit is just under £UK 3000 + 20% VAT (sales tax).
There is another even more interesting potential solution produced as a research project in Dr. Aldo Faisal's neuroscience lab at Imperial College, London. This is a head worn rig and the prototype hammered his lab's budget to the tune of about £UK 50 (inc sales tax !) for the bits. OK, the only one made to date is a prototype and it sure as hell isn't pretty - bare, uncovered circuit boards and camera mounts - but apparently Dr. Faisal, as head of the lab, was amazed at its functionality. I would say, looking at it, that the material cost to 'package' it neatly and produce it would be under £UK 100, so they could profitably be made and sold at around £UK 250 - 300.
The link is to an article from CNN, but there is sufficient info in the article to enable you to find virtually anything else you want to know about this device.
All this interest started because somebody said to me 'How do you make the web more accessible to people with disabilities ?'. The problem is that there is a huge range of disability types. 'Disability' covers people like my late Auntie May who essentially dared the motoring populatiion of Edinburgh to run her down when she was crossing the road ( she had Parkinsons ), through my wife's sister who is confined to a wheelchair but otherwise has no problems with computers, to people who are paralysed from the neck down. And that doesn't include people like my blind neighbour.
How do you make the web accessible to people who are blind or at least very severely visually impaired ? Yes, I know you can get braille keyboards and braille printers but I can't think of any mainstream web-sites which can interface in braille, or even merely speech. I run a couple of small web-sites for Clubs I am involved with and happily, blind members is not one of my problems. The only solution I can think of would be to add in audio clips for everything, and what that would do to the size of the web-site I shudder to think. At the least, it would be the end of my free hosting arrangements for these sites.