Xiaomi (Yuwell) Pulse Oxymeter

This was listed as Xiaomi, but is made by Yuwell model YX303. It's a standalone unit powered by 2 AAA batteries and sized 58 x 32 x 34 mm.

The unit is hinged so you place you finger in between the two halves and then turn the unit on. The colour OLED will turn on and the screen will show a waveform and your pulse rate and blood oxygen level (pO2). It takes a few seconds to get a reading.

Quick pressing the button again will rotate the display 90 degrees, then again another 90 (so 180), again 270 and again back to the start.

If the finger is removed, the unit will indicate "sensor off" and turn itself off.

As a Xiaomi product it's at the upper end of the price range and there are other cheaper units out there. It's available on import for around £20 (not available through the UK site).