Support@Seestar we can't guarantee that every user will have power and the time is accurate when they finish their planned shooting
The device already shuts down at around 5%; it just needs to shut down towards the west instead of homing back to the home position. As for time inaccuracies I guess you might be thinking of a time change like Daylight Time Saving while shooting, right? The devices should already take account of that and even in the extreme case that the device suddenly gets an updated time, you can always skip that and point to the west no matter what?
I guess that the only issue left is a sudden compass calibration problem, but I would bet that the devices have a mapped starting (a.k.a. "home") position and know how many "steps" they have moved around their respective two axes. You could program the device to keep that in memory at startup and know that no matter what, west is at position X and Y and that is the position at the end of a planned shoot or at dawn.