I don’t know if you would count this as being “suspicious” per se, but...

I also told him that for his own security he should have it checked out. I added that I know a guy who is really good at security system stuff, and he can check out his system for him if he wants. He’ll even change the door locks for him, too.

I don’t know what it is, sorry. Personally, I think it looks a bit like a microchip. It’s the first time I’ve seen anything like this.