There are two ways around the key on requirement. One is to change plans to Mobley/ATT plan same as OnStar. One can buy the AC adapter for the wifi unit and bang... done BUT.... their unit doesn't handle the LTE speeds well.
Second Onstar Option would be to keep key on door locked....Also okay if.... there is a way to keep the batter charged up. I checked on an RV sight and they are way ahead on this... one guy attached a battery tender under the hood on wall ...small unit and the AC plug out the front like a core heater. Here is his post:
Yes, the tender attached with circle ring connectors to small screwed terminal already on the battery terminals. It stays connected all of the time. The unit is about the size of a small durable laptop power supply has a minimal LED status readout and is velcro'ed to a flat surface in the engine bay. It is unaffected by the operation of the truck it also has a quick disconnect cable for removal if need be. The truck also doesn't know or care the tender is there. It has a peak 12V of 6 Amp bulk and monitors battery state then falls back to float and pulsing float charge so it could be left plugged in indefinitely with no over-charging harm. The pulsing is said to prevent sulfur crystals on flooded type cells. Would also work for extended storage of coach house batteries etc.. Is comparable with flooded, AGM, and lithium cells. Yes 110V very low current draw.
So I am now looking for a tender like this (I am not a member on the RV site). Any suggestions let me know.
2016 Colorado Duramax LT CyberGray Longbox 4WD