This photo (38mm watch worn on my right wrist) shows the Dexcom receiver. This is the unit that receives the signal from the transmitter unit attached to the subdermal sensor.
The transmitter is paired to an iPhone using Bluetooth LE. The Dexcom Share app, installed on the phone, has a component (pictured here and in the original post up top) that can also display the current reading on the watch. There is a lag of about one to three seconds before the current reading appears.
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Some insurance may cover it. Call the member number on the back of your insurance card and talk with a rep, or ask your diabetes care provider. Dexcom CGMs are available for adults and pediatric applications.
I love having the ability to check my glucose levels at any time and have since I got a CGM in 2013. I got the Share version of the receiver when the original receiver failed recently.