I have been using this application now for the last month. It surpasses the two other HRV applications that I tried. Things that really standout:
1) Easy to use
2) Actionable advice
3) The creator has spent a great amount of effort to educate users through his blog
However, what I really love is you can download your data in raw form straight to excel for your own analysis. You should own your data and this app lets you while others do not.
I highly recommend HRV4Training (and the blog/website that goes along with it). After I have used it longer (6+ months as opposed to 1 month) I will return to update my review. Until then, download it, use it and train/recover smarter.
Ben P Metcalf about HRV4Training