Ari Bixhorn just did an excellent demo showing some of the capabilities of Indigo. He wrote a service that sends a message to his Pocket PC device based on events in Windows Media Center.
For the demo, he used an example of his second grader watching Jerry Springer at home while he's at work. When the Springer show came on, he recieved a message on his Pocket PC based on the rating of the show. He then sent a message back to the television, “Your busted!” and changed the channel to Spongebob Squarepants.
To take the demo further, an Indigo service then polled the Amazon web services to see if they had items related to Spongebob. They did, and so while watching his show, little Jake can select items from Amazon and place them in his wish list. When Ari's at the toy store shopping for his birthday, he can access Jake's wish list on his PocketPC and purchase the items.
Other Media Center demos included a service that retrieved weather information when it detected that golf was on, and another that allows the viewer to purchase all of the materials needed to complete a project shown on a home improvement project.
Cool technology, but it's easy to see the future of combining television viewing and marketing.