"Until recently no mobile-based product could display DFA a1 in real-time using an off the shelf consumer device" ... well, that has changed
Check out how you can use the Heart Rate Variability Logger app to estimate the aerobic threshold non-invasively, in the British Journal of Sports Medicine:
"From laboratory to roadside: Real-time assessment and monitoring of the aerobic threshold in endurance-typed sports"
Thank you Thomas and Bruce for involving me in this project, I've really enjoyed working with you and making your scientific work more accessible via this app
More to come...