I have a glucowatch. I haven't used it for a couple of years, but dug it out of the box yesterday to try to get a couple of 12-hour long trend graphs, to aid me in getting some sort of a grip on my control. I am unable, however, to get hold of any autosensors (The sticky pads which connect you to the watch and cost approx. £50 for 16). The watch is ok for tracking trends in your bm control, but the sensors cause an itchy rash which can last for a couple of weeks after you remove the watch from your skin, and as soon as you start to sweat, it skips readings. This is not really very helpful, especially if you, like me, sweat when going into a hypo. This is why it struggles with hypos - not because of the low blood sugar level, but because of the perspiration. The other thing is that as it uses interstitial fluid (the fluid that fills up a blister when you burn yourself), there is actually a lag between the reading you are given by the watch and your BLOOD sugar level. I'm not sure, but I think the lag could be as much as 15 minutes. Therefore, unless you are dropping gradually, and the alarm lets you know there's a hypo on its way, you will already have your hypo warnings 15 to 20 mins before the watch tells you you're low. If, like me, you don't get consistent hypo warnings and can in fact go into a severe hypo with no warnings, the watch is not going to be very helpful.
If anyone has other experiences, feel free to contradict me, but this was my experience with the thing. Not cheap, either!