Israeli startup Eco-Fusion has developed Serenita – an app that measures and can lower your stress level. Cover your smartphone lens with a finger to measure heartrate, blood flow, and respiration. Serenita’s 5-minute personalized breathing exercise then visibly reduces your stress.
https://www.ynetnews.com/articles/0,7340,L-4735610,00.html https://www.eco-fusion.com/serenita/