My 370 doesn't have a wear sensor. Not sure if any do?
Wheel off, get your head into the wheel well, and look into the aperture on the outside of the caliper (where the pads are fitted and removed from) A torch will help. The anti rattle is partly in the way but you can see pad thickness.
I guess you could also do it with a small mirror or even a phone camera with the wheel on?
But it's only a couple of mins to remove wheel and then remove the pads, it's very simple, so I tend to remove, clean, inspect, and refit or replace pads on my cars annually. JMHO.