You can sign up for the field trial here. If you are already part of it, I don't think you have to sign up again. Still, check to make sure.
Searching for "my purchases" shows tracking information and receipts for online purchases based on receipts in your inbox.
Searching for "my events" shows events from Gmail.
Searching for "my hotel reservation" brings up the hotel information that you have in your inbox, such as location, dates, and check out times.
Searching "my flights" brings up detailed information about upcoming flights that you have.