Muckrack.com aggregates journalists on Twitter into a single feed. It’s fairly comprehensive and nicely laid out. Will definitely be going back and subscribing.
You can’t really search by city and hopefully they’ll add more sources to the list – you’ll see what I mean when you go to the site; for example, you can break things down by news outlet (NY Times or Huff Post, etc.), but after that there isn’t much funcionality.
Seems like a no brainer would be for a company to start this type of service by city (like the Gothamist network but Twitter instead of blogs) to aggregate news, government offices, traffic, arts events, famous citizens, etc. After the site gets set up you really wouldn’t have to do much beyond general maintenance. Any investors would to help me make this reality?