Siri is that very cool personal assistant app. It allows you to ask questions that the app sends (as your voice data) to a server where it is recognized. The query is then sent off to a series of search engines to find an answer, which is finally returned to the user. You can ask for things like the best area pizza shop, the status of an arriving flight or the weather in Omaha. The speech recognition in the app comes from Nuance, the company that developed Dragon Dictation and Dragon Search.
Last year, Apple bought Siri, and it seems likely that the tech will find its way into Apple products, especially iDevices. Siri is a very clever app, and it has always made a great demo on my iPhone. To have it built into iOS would be great. It appears Apple is trying to wean itself off Google services, like Search and Maps, and Siri would be a step in that direction. If you don't have it already and want to play with Siri, you can get it free at the App Store. Prepare to be impressed.