At least my parents church has the decency to give first time visitors a free 6oz cup of coffee.
I decided a long time ago that if I ever walk in and don't recognize anyone, and someone thinks I'm a visitor who didn't grow up there, I'm going to start quoting Bible verses about how selling shit inside the church is wrong and I would be channeling the righteous anger of Jesus himself if I flipped all their tables and whipped them.
Unfortunately despite the fact that I have been there twice in 10 years, people still recognize me.
Why not just tattoo a number on their arm?
I'm sure there's no possibility that subdermal trackers would ever be used in shitty ways.