I have not followed Dexcom's instructions and have put my receiver through the xray machine. The newer technology scanner finds my sensor and my pod from my insulin pump so I have to be checked. My experience has been as soon as the words "medical device" leave my lips, the TSA agents back off. They tell me I do not have to show them the devices however they do ask me to touch the device and then they swab my hand for explosives testing.
I have only flown internationnally to Canada. Some airports still use the magnometers (Toronto City Island comes to mind) and the sensor never shows up. The pod usually doesn't show up either.