The FIT Treadmill Score is easily attainable from any standard exercise test (e.g., the Bruce Protocol) and translates basic treadmill performance measures into a fitness-related mortality risk score.
This app uses your demographics data stored in the Health app to calculate your FIT Score, as described in "Maximal Exercise Testing Variables and 10-Year Survival: Fitness Risk Score Derivation From the FIT Project" by Ahmed, Haitham M. et al.