Stock Data Streams

I was wonder if anyone knew where stock applications got the data for the stock information that they display in apps? I'm looking to write a simple stock app for android and this seems to be biggest hurdle as to where to get the data from. Do most apps just parse popular web sites like yahoo or google for the data or is there some live data stream with the information?

After some of my own research I found a guide on how to pull from Yahoo Finance:
http://www.gummy-stuff.org/Yahoo-data.htm