They're not unique to NYPD. Cops in New Jersey have them too and I'm sure others.
In my highly corrupt country, it's enough to tell the officer you know person so-and-so. They might ask you a question or two, or even threaten to call the person you claim to know, but they rarely do.
Do they exist somewhere else?
The police have wide discretion to issue a warning instead of a fine in most countries as far as I know. But these cards seem to be unique to NYPD. I don't mean that corruption doesn't exist elsewhere but usually it's a little less obvious!