The site EveryBlock.com has been around for awhile, but now launched a feature called Notify Your Neighbors. Post something that you saw or something that is happening, and anyone in that neighborhood, block or zip code will be notified next time they log on the web or use the new EveryBlock iPhone app.
Below is a screenshot of how you can send notifications to your "block" on the iPhone app. It sounds like a pretty handy micronews feed... just as long as people use it.
The service is now available in each EveryBlock city: Atlanta, Boston, Charlotte, Chicago, Dallas, Detroit, Houston, Los Angeles, Miami, New York, Philadelphia, San Francisco, San Jose, Seattle and Washington, D.C.