Child proofing a presence sensor

so my smartthings presence sensors have been great, except the one assign to my teen. Noticed in the logs he had not been home for for over a day & I asked him for his fob, and I got the pieces of what was left of it. needless to say it is being replaced, and I am going to add some increased durability.

I have some ideas, layer of duct tape and then shrink wrap it a few times or encapsulate it in a few layers of rubber dip. just trying to think of something simple, that can be cut back open/redone for battery changes.

wondering if any others have had this experience or have some insight on how I may protect it better from the teen

here is what iI ended up doing, rummaging around the garage I found Truck Bed Liner from when I painted my truck & so decided to run with it. Skeptical it will not be the final version, however I am seeing how it hold up before I just go ahead and shrink wrap them.

https://drive.google.com/file/d/0BwtX8oN3PGb_bDZ2eHBzQlpseGM/view?usp=sharing