Mathematical Birth Control

Shanie • I am… a 21 year old theatre major. Socially awkward. Currently dating the potential dork of my life.…yep ¯\_(ツ)_/¯
This is a new revelation to me: so, Swedish nuclear physicist, Elina Berglund, created a birth control app that is the first to be approved as a contraceptive. It uses your temperature(taken under your tongue) and a mathematical algorithm to determine if you're fertile or not. 
What do you ladies think?
Edit: The app is called Natural Cycles and it's still seeking approval from the FDA in the USA, but it's available in the U.K. and Sweden.