What an interesting solution to help women (and men) better protect themselves against rape drugs. I like how the developers made sure that the end users can use the product discretely. By packaging it as a napkin, anyone can test their drinks without letting the people around them know what they're doing.
After all, you wouldn't want would-be attackers to know that you're on to them and give them a chance to escape. Plus, no one wants to appear paranoid or hurt their friends/co-workers feelings by making it appear like you don't trust them when they see you testing your drinks around them.
Yap, I think that is the coolest advantage of this napkin because would-be attackers would not know about it.