ProPublica reporter/developer here.. There's a tool embedded in the article to see if your carrier is setting a tracking header.

We also published a follow-up about how AT&T has said they will stop using the header: http://www.propublica.org/article/att-stops-using-undeletabl...

My provider, TracFone, appears to be sending beacons. This is a low cost pay-as-you-go service that buys airtime from the big carriers. My particular phone uses the Verizon network.

Is there a way to opt out of this?