Pulse Oximeters

I had never heard of an oximeter before today, but some online research has taught me that pulse oximeters are small devices that can measure not only your pulse rate, but the oxygen saturation level of your haemoglobin (which apparently should ideally be over 95%).
Haemoglobin levels are traditionally measured via a tiny blood sample taken by a pin-prick to the ear or finger, the oximeter measures via a non-invasive optical method using LED's and measuring the rate of light absorption. The technology has been in existence since the 1940's although not widely adopted until more recently.
The advantage of the oximeter is that it can constantly monitor over a fixed period whereas a spot sample can only give you a single result unless you want to turn the patients ear or finger into a pin-cushion.