The S10-line from Samsung has that feature so it's certainly not impossible

There was speculation when the 8/X came out that they would have that feature. I would love it. Too many times, I have forgotten to charge my watch in the morning and only remember when I go to to run errands and see it in red. It’s not like you can just plug it into a lightning cable in the car and top off. I refuse to get a watch charger just for the car.

That's not possible (and probably ill advised as the watch will usually outlast the phone) - however it is possible to charge your devices from an iPad.