The SmartNAV is a clever little gadget that sits on top of your monitor and converts your head movement into mouse movement. You can read all about it on their website. In my case the only part of my body that I can move is my head, so it is perfect for me. I remember saying to myself when I first saw their website that this seems too good to be true - especially at that price !!
It works by illuminating my face with infra-red light (which is completely invisible and does not interact with any of my equipment). Then it reflects off a small reflective self-adhesive dot (in my case stuck on an old pair of sunglasses without lenses) and is picked up by a small camera in the unit itself. Internal circuitery then converts this signal to mouse movement. The actual mouse still remains active and moving it will override the Smartnav momentarily or pressing F9 will permanently disable it.
I have been using it since 2002 and has worked faultlessly. Only recently (early 2007) my unit has finally given up and I bought the newer SmartNAV3. Unfortunately the basic model has now been discontinued (apparently they don`t have many requests for it) and the manufacturer is concentrating on the other models (which are also more expensive) that have a socket for fitting external switches to provide mouse button clicks (I use dwell clicking - Point N` Click). Since I was looking for the basic model (and postage from USA was extremely expensive) I looked for a supplier in UK and found one : Techready . In fact I ended up buying two as I needed the other one for my Tablet PC on my wheelchair. With this configuration I can do practically anything on the computer - this website was all done by me with this setup.
This application (Tabet PC on wheelchair) highlited a problem : although I have used the SmartNAV in most light situations, it was always indoors and it did not work outdoors. I didn`t expect it to work in bright sunlight where even the lcd display of my Tablet PC is illegible, but it didn`t work even in the shade. I contacted the manufacturer and they confirmed problems outdoors, so if you intend to use it outdoors this is not for you.