As a professor, researcher, and sports performance coach, I was really excited to finally get my hands on this! Monitoring HRV and state of readiness is the wave of the future for creating specialized and individualized training programs. PROS: so simple to use. Plug it in, strap on the HR monitor, lay and relax, and let the app work. Also love how it tracks your HR and HRV over time, so you can see your trends over time. Lastly, the accompanying book is great and detailed. Although I think it could be too much for someone without an exercise science background. And from what I've read and heard, the results are valid and reliable. CONS: this would be an AWESOME app is you could create multiple profiles and see their trends over time. Right now, it's only set up for one person per device. So for someone like me that works with teams and classes, I technically would need 30+ iPads/iPhones so that EACH athlete/student could see their trends over time. Not cost-effective. If only this app could let you create several profiles on ONE device so I can test Athlete 1, save their scores, switch profiles to Athlete 2's, save scores, etc. This is the biggest negative of this app and hopefully can be added with a future update. If Joel can figure out how we can track a group of athletes/students on ONE device, that would make this a PERFECT app for HRV monitoring.