This is what real-time search and the future of advertising is all about. This is were context matching, location based services converge. Whoever is the best at matching a context of a particular user with any offering, product and service will be the big winner in online advertising (which I guess is the monetization model for Siri).
You simply speak into the phone with a request like, “Find something to do in San Francisco this weekend.” It turns your speech to text and pushes your request out to an appropriate service on the Web such as Eventful or Citysearch, in this case. It not only attempts to bring you back the appropriate information based on context, time of day, and your location, but with your permission can go ahead and make reservations or buy tickets as well. (Read our extensive first-look coverage from last year or watch this sneak-peak video)
Read more here: Siri’s IPhone App Puts A Personal Assistant In Your Pocket