Personalized RSS feeds. The article from Techcrunch talks about the new web alert service in the market - Trackle and it's usefulness as a tracking tool.
Trackle differentiates itself by providing highly customizable alerts and tracking system. For instance, if anyone wants to buy a particular camera and is not willing to spend more than $200 on it, Trackle tracks the price change and sends across alerts of the price reached $ 200 or below.
This is just one of the many alerts that Trackle makes available. There are many features and alerts that one can customize using Trackle.
It has the feature for tracking crime in your neighborhood also.