These Norelco Emergency Response boxes aren't nearly as prominent as they used to be (in the 1980s, there were over 1,900 in the city), but where they remain, they still work. Cell phones have rendered them somewhat obsolete, though you still see them around, presumably where they haven't been vandalized beyond repair or removed for new construction. I saw this one along Sutter Ave in East New York, and it struck me because it's older than most (the link above takes you to another blogger's image of a newer one).
I couldn't find any statistics on how much use they get, but they probably also serve a purpose as deterrents to crime.
In separate news, the First Saturdays afterparty at Franklin Park rocked. They're now offering a trivia night on Mondays, too, if you've sufficiently recovered from Saturday.