Specifically, as both the title and pages 2 and 3 say, it's a "Yokkyuu Fuman Hitozuma Radar," which basically means "Horny Housewife Radar." ("Frustrated Wives Radar") She does end up divorcing her husband and then later marrying the main guy, so he doesn't need the device and gives it to his virgin cousin, so that his cousin might end up achieving his original (and his dad's) dream of a "(other men's) wives harem" ... but that, as it says, "is another story."