A pulse oximeter which goes on your fingertip
Once switched on with the little button on the front, the screen lights up green and starts to take your pulse and oxygen in the bloodstream.
From what I’ve found its quite accurate but every now and again it will have an anomalous result for a second or two then go back.
if no input is detected it will switch off after a couple of minutes.
Make sure when you use it your finger is all the way to the end as this will then pick up the heart rate better.
This is a great way to monitor your heart rate in an easy way as well as your oxygen saturation.