"In focus groups, the biggest thing they said to us was it made them safer, because if you are in a public space you know someone's watching."

This is a rather ridiculous comment. Although people might be watching, they are unlikely to report what they see, precisely because they assume that someone else will take care of it. On seeing this, I recalled classic studies in psychology which found that the likelihood of reporting (a crime) was inversely proportional to the number of witnesses. I went looking, and quickly found a lead:

Forcing the Bystander to Get Involved: A Case for a Statute Requiring Witnesses to Report Crime

In the footnotes on the first page, I found what I was looking for: Kitty Genovese:

Catherine Susan Genovese (July 7, 1935 — March 13, 1964), commonly known as Kitty Genovese, was a New York City woman who was stabbed to death near her home in the Kew Gardens section of Queens, New York. The circumstances of her murder and the apparent reaction of her neighbors were reported by a newspaper article published two weeks later and prompted investigation into the psychological phenomenon that became known as the bystander effect or "Genovese syndrome."

Perhaps they could get somewhere if they made it into a game, offering a sizable bounty for good tips that result in arrests, and penalizing callers for bad tips. To draw viewers in relatively safe neighborhoods, they could even seed the pot, guaranteeing at least one prime-time witnessable crime per night.