In his New York Civic blog today, Henry Stern suggests that the City of New York have a system for alerting cell phone (and landline phone) users to bad weather, serious accidents and traffic delays. It's a good idea, especially if one can opt out of it should it be overused. A possible danger is that in a real emergency the City's alert would overload the phone networks at precisely the time they are most needed. If the messages are very brief that would perhaps avert the overload danger.
CityEconomist suggests a less-intrusive and less-risky Reverse 911 option that would not preclude the phone option. Why doesn't the Mayor's Office of Emergency Management send out short alerts? OEM already has an email list for sending press releases (I get some of them) and could have sent out alerts regarding the Con Ed explosion and the Brooklyn tornado, in addition to the extensive information it posts passively on its City website.