Here are a few of our favorite applications to help with NFP. If you know of any other ones that we should be aware of, please leave a comment below!
FemCal: Period and Ovulation Calculator
Free for the Andriod (Symptothermal Method application)
$2.99 a month or $11.99 for 6 months (For Billings)
$9.99 one time fee. Tracks cervical mucus, BBT, saliva ferning, urinary estrogen and LH, and more.