Last week NASDAQ released version two of their Market Replay AIR application and added a couple of interesting features as well as provided some details of how the service works. Market Replay is available as a paid service and the downloadable client comes with the service. The goal of the application is to provide a large amount of data to traders and hobbyists who want to explore market conditions over a specific time frame. The new version of the application includes trades so you can actually drill down at a millisecond level to see bid and ask prices for all of the major exchanges as well as when trades happen.
NASDAQ is actually using Amazon S3 to store and serve data down to the client. They store the stock data in 10 minute chunks on S3 and then when the AIR client requests it, they grab those 10 minute files and download them to the users machine. That makes the data available offline so you can look through the data regardless of whether you have an internet connection or not. And since you have the raw data, you can do almost anything with it.
The new version uses Flex's charting components to provide a graphical interface for moving through the timeline and replaying what happened. It's skinned to look very much like a trading screen and as the user moves through the replay, the bid and ask prices for the various exchanges will change so you can get a picture of exactly what happened to the market. You can also dump any of the data directly into an Excel file for parsing or manipulating it on your own.
All in all it's a very good application and a good use case for combining services like Amazon S3 with clients like Adobe AIR. It also provides a very dynamic, engaging way to do stock research.