Breathalyzer - reviews

What is this Watson formula? I haven't heard of it. I wish someone would give me a sensible answer as to what this thing is. Somehow a regular breathalyzer seems more trustworthy. My husband in a taxi company has one - Sititek CA20F, brought it home, pretty decent model, but more professional. And I would like to buy something like that for my personal use, you can also get something simpler.