I just downloaded an app[1] that measures heartbeat rate by taking video of a fingertip. I was stunned by the brilliance of the application, how ubiquitous vid

I just downloaded an app[1] that measures heartbeat rate by taking video of a fingertip. I was stunned by the brilliance of the application, how ubiquitous video sensors can replace other senses. There's something else to discuss here: We have a recently published paper from MIT, including mathematical details of the process; and at the same time a stack of closed-source commercial applications already in the market with slick interfaces. Are they using the same technique? Is one app-maker trawling preprints for app ideas? Are many app-makers copying one pioneering app-maker? [1] https://play.google.com/store/apps/details?id=com.macropinch.hydra.android&feature=related_apps https://play.google.com/store/apps/details?id=com.macropinch... but there are many similar apps.