I don't know of anything commercial, at least not something that's being sold over here.
Both my cats go out, and they have their ears tattoed, wear a collar with my phone number, and generally come when I call them.
That's one of the reasons why I let them go out at all: they come when I call them.
They go to the neighbors most of the time, and when I hear Rudie being in a fight (he usually screams very loudly), a simple call lets him know I'm around and he runs to me. Sometimes in the summer he's out all night, and that's terrible. I don't sleep at all, so I know what you're going through when your cat is gone and you don't know where he is.