Is a period tracker and ovulation app that uses science and data to help you discover the unique patterns in your menstrual cycle. Use Clue to remind you about your period, PMS, ovulation and fertility.
https://play.google.com/store/apps/details?id=com.clue.android
or
http://helloclue.com/
or
https://itunes.apple.com/us/app/clue-period-ovulation-tracker/id657189652
Do menstrual cycles sync?
http://blog.helloclue.com/post/158185861431/do-menstrual-cycles-sync-unlikely-finds-clue
Can We Finally Kill the Myth About Women’s Periods Syncing Up?
http://vitals.lifehacker.com/can-we-finally-kill-the-myth-about-women-s-periods-sync-1794220779