For battery powered things like contact sensors I just seal the led hole and the edges then use a razor blade to open it. I usually run cat 6 to contact sensors and power them with a POE switch hate changing batteries. I only have three devices that are fully exposed to the elements. two contact sensors and the door bell button. The door bell button is powered by 24v poe with resistors to drop the voltage,
on a side note the Door bell button hates being mounted to stainless Steel I couldn't get a signal at all when mounting directly to the Box.