Let's clarify "irregular". An "irregular" CYCLE Length means that they have a cycle length that varies. OV-Watch can be used for those women and it will work perfectly as long as the cycle is under 39 days.
If they have an IRREGULAR cycle, that means that they don't always ovulate. In those cycles, the information that ov-watch gives will vary on what is going on hormonally with the woman. IF she is not ovulating because she has high fsh (for instance anyone in their 40's or anyone with POF) then the watch will read NF (not fertile) all month. It will not see a surge. In the event that it is a cyclical pattern and they are fertile, they have an LH surge and the estrogen just doesn't ramp up high enough (like in the case of LUFS syndrome) then, it may read fertile because the body was ramping up to ovulate and her body was fertile, but she never ovulated.
In the case of the untreated PCOS woman, I don't recommend them wasting their time and money on any product until they are taking metformin and clomid/femera, as they are NOT ovulating and any effort to get pregnant will only result in disappointment. If they are on clomid and they are ovulating then OV-watch is the BEST device for them. We have lots of PCOS success stories.