I cannot answer with regards API.
But I do know about trading news.
Quite fascinated by it. Here's one of many private youtube videos I have in my collection - for self-education, the very occasional share, and just for the sake of historical records.
http://www.youtube.com/watch?v=zB_SyY5KFaI
The point I want to make with this is how quickly the market responds to breaking news - faster than most people realise. The text-based news feed displayed there is the Interactive Broker News Platform, streaming DOW JONES GLOBAL MARKETS NEWS (That is their premium text based service as far as I know, around $250/month, depending who you ask).
I tried some other platforms, but my conclusions were that you are depending on 3 actual sources of news, really:
Dow Jones (2 stars out of 5)
Reuters terminal (5 stars out of 5, but $15k/year?)
Bloomberg terminal (5 starts out of 5, but $15k/year?)
Dow Jones can be access via third parties such as the Interactive Broker News Platform, but Reuters and Bloomberg breaking news can only be accessed via their respective terminals. For Reuters, that was previously not the case, but is today (I am told).
So in conclusion, I think you really need Reuters + Bloomberg to profit.
If I had access to a Bloomberg terminal, and had the patience to stare at the breaking news all day long, there is free money to be made if you are ready to click buy/sell in the correct market within 3 seconds. 3 or 4 seconds is all it takes for any of several SQUAWK Boxes to repeat the news, and then every prop trader and his dog is all over it.
Dunno if any help to you. Just my thoughts there. Typically downbeat/defeatist/realistic(?) as is the case on trading forums I'm afraid.
Goodluck