-Clinically Accurate Basal Body Thermometer for Natural Family Planning — Use iProvens BBT to detect your ovulation pattern and pinpoint your fertile window. Special chip for accurate readings to 1/100th degree. -Reading in 60 seconds, faster than any other BBT — The ovulation thermometer has a small tip that warms up quicker and therefore delivers an accurate reading of your real body temperature faster. Manually enter your temperature in any ovulation app — The iProven Basal Body Thermometer does not synchronize with an app, but you can manually enter your data in any ovulation app. Or print the chart and track your cycle on paper! -Easily replace the battery in 4 steps — When the empty battery symbol is displayed, this is how you can replace it: open the cap; hold the battery case between your fingers and remove the battery with a needle; insert a new battery with the '-'sign facing up; put the cap back on.