Hello! Started training finally. I used a Qarudio pulse oximeter which does both O2 and HR in real time. Seemed to work very well, although I noticed that if I also connected another HR device, the pulse ox for the Quardio would stop working. Weird. Quardio is a great brand for automatic blood pressure coughs, which is why i tried their finger pulse ox for this application. If you want to just get one device that does both O2 and HR this seems to work well! Cheers.