Fairly reliable overall

Oximeter very easy to use even without iPhone. It recharges quickly through a USB port (cable supplied, thank you!). The object is small, so fits easily into a pocket or bag.
Once the finger housed on the red lens inside of the case, the result is displayed after about thirty seconds. This gives the rate of oxygen in the blood and the number of heart beats per minute.
Being connected to the iPhone lets just to follow up.
The device itself to me perfectly serious air it's like at the hospital.