Google Now is powerful, but did you know that it will alert you about price changes to hotel reservations you've booked in the future?
As you know, with most hotels, you have 24-48 hour prior cancellation policies. So if you find a better price between now and your hotel stay, you can likely cancel your reservation and rebook for the better price.
Google Now is able to read your emails, find your reservations and likely through Google Hotel Finder, scan for price changes. It can then alert you as it finds lower cost pricing for the same hotel reservation you placed.
Brian White shared such a case on Google+ and was quite pleased, he said:
Thank you, Google! Is this card useful? Hell, yeah!
Forum discussion at Google+.
Update: I am told this is just a test.
