I'm on a JetBlue flight and noticed a cable running from the gate / gangway into the plane, which appeared to be labeled "Cabin Temperature Probe" or something to that effect. The cable is draped over the divider in front of the first row of seats. Further, the console outside the plane appeared to have only a single yellow light (which was off), no display or additional controls.
What is this for? It seems like a sensor actually installed in the plane would be more accurate (it would work even when the door is closed). As is, I imagine the probe is picking up much more ambient air than cabin air.