I bought the biostrap for the purposes of monitoring my sleep. So far it has done an exemplary job of accurately recording my sleep. However, I have had a couple of nights where it has not recorded despite it being charged and on my write securely. I have raised this issue with bootstrap support and they have been great about responding and escalating it to their engineers. Overall, it seems to be a great device, reasonably priced, has a great accompanying app., and does not require a subscription. I also like that the strap is not a watch, as I am attached to my automatic wrist watch & don't want to replace it.