K.
Hi C.,
There are lots of ways to predict ovulation - the OV watch works the same way the "spit" test works - it checks for salt concentrations in your body, which rise right before ovulation. There are other (much cheaper) fertility monitors out there that basically consist of a glass slide and a magnifying glass. You spit on them and let it dry; if you see a "ferning" pattern, your salts are up and you may ovulate.
When we were TTC I had very long (100+ day) cycles and I was just temping and checking cervical fluid. This method worked well for us (I got preg my 2nd cycle, though that was 6 months later!) and because I was charting my temps I had an exact date of conception. (I also loved www.fertilityfriend.com)
Anyway, if you're looking at the OV Watch and don't mind doing a little extra work, I'd say get one of the "spit kits" instead - should work just as well and it will be way cheaper.
Another good recomendation - esp. if you tend to have long/irregular cycles - is to pick up a copy of "Taking Charge of your Fertility". This is a great book and cleared up a lot of mysteries for me - and I considered myself reasonably well educated on the subject!
Good luck!!
-K.