Ovulation Watch

Dr. Reichman writes:
Dear Colleagues,
The latest in ovulation testing is the Ovulation watch, which can predict 4-5 days prior to ovulation and significantly increase "fertile" days beyond existing testing. It works by sensing chloride ions from the sweat of the body. There is no color change, but a chemical analysis occurs. Rabbis will likely be asked about the permissibility of wearing such a watch on Shabbos. For more info, see http://www.ovwatch.com/ We will have to clarify the nature of the mechanism of action in order to answer the shabbos question.
ER
Any thoughts/suggestions?