This recently released fingertip pulse oximeter from Swedish MedAir AB is now available over the counter, for about $200.
Some of the features, taken from the product page:
Durable: Built to survive multiple drops onto a hard surface from 1 meter (39 inches).
Tested Accuracy: Readings you can trust. OxyCheck accuracy testing was conducted at a Hypoxia Research Laboratory. Every product claim is supported by extensive independent testing.
Fast: OxyCheck obtains results in less than 10 seconds. Why wait 20 to 30 seconds for results?
Reliable automatic On/Off mechanism: OxyCheck reliably turns on with finger insertion and turns off with finger removal. No need to worry about draining the batteries due to failure to turn off.
Works on widest range of patients: Works on pediatric to large adult fingers 8mm to 26mm (0.3-1.0 inch) thickness.
Water resistant: Passes IPX2 water ingress test.