The oximeter proved interesting. Used it and thought I must be dead. Sat down and hyperventilated a bit and wondered why what I thought was oxi levels went down.
Then I read the instructions. Moving bar graph next to the oxi reading. Thought that was pulse rate and wondered what it was doing at 90+++. Looked at the right way, pulse 63 sitting, oxy 94-95 if I hyperventilate a bit. If covid goes strange ways people will be hyperventilating. £15 well spent really even if no one here needs it.
Amazon have a rush delivery service for these and a stick on label sealing them stating they can not be returned once opened. I was surprised how early it arrived.