I am currently in the process of wiring up a few switches to turn off my dashcams (my cellink b has a switch but it's quite difficult to reach) but this thought has crossed my mind, because on some occasions I have forgot to turn off the cellink when not needed.
The main issue with this is whatever is checking for wifi / bt / gps will need power it self, and depending on how the dashcam / battery is switched on/off, there may be a power requirement there as well. I think some car gps trackers have outputs so you could potentially engineer something that way.
Also I always thought a raspberry pi / arduino would use too much power although by turning off various bits of the hardware some people have managed to get some really low power draws.