I'm wondering if anyone knows of a PIR suitable for mounting on the outside of a vehicle. It's for a conversion van to be used in remote areas where bears live, and the owner wants to trigger the alarm when a large carnivore approaches the van. For those unaware, a van tends to have food odors, and bears can do serious damage to a vehicle going after the slightest scent of food.
The challenge is that in addition to being rated for use outside, it needs to be fairly streamlined so as to not be too noisy while driving, or tend to get ripped off by branches when four-wheeling.
I'm thinking a low profile surface-mount might work, but I've never seen one quite like this.