This got me to wondering about how often I walk over the scene of a murder. Can you imagine if permanently left at every murder scene was a small plaque with this information? It would be a very interesting project to get a huge team of volunteers, and to tag the city with all of these.

I remember one night walking back from the bar in Cambridge MA, we crossed a spot where there was quite a bit of blood spattered about. Something bad had happened there within the previous hour or so.

Actually, that made me recall one night stepping out of a cab in Boston where a small crowd of people were just starting to gather around a man that had been pushed out of a car, then shot, just moments before we arrived. We then went to the 7-11, and minutes later, police swept through, and then left. The guy was killed just outside of my friend's apartment. Had we been 10 minutes earlier, or 30 minutes later, we would have never known it had occurred.

It would be interesting to do a project with Google Glass, where you labeled the city with crime.