Clue - period and cycle tracker
"OK - hold tight - this one's about LADY BITS.
Or, specifically, how to keep track of 'em. There are a whole bunch of apps out there that do the same thing, but Clue does it with better UX, seriously beautiful design, and a level of finish that nothing out there seems to manage ... plus, NOT A BUTTERFLY IN SIGHT.
It helps you keep track of your monthly cycle, and all that comes with that (whether it's getting pregnant, not getting pregnant, or just getting more in tune with your body). Just make sure you manage your settings: I've had an ovulation alert pop up in the middle of a meeting ... #awkward."