We were one of the companies to support this during the launch announcement today, and we've been playing with it for the past month or so. It's an awesome feature for transactional emails that require a quick action to be performed - we use it for task notification emails where you can check off a task as complete right within the email client. It's based on an open standard, and plain old HTTP POST so not specifically tied to Gmail.
Again, what is the difference between this and clicking a link? Instead of showing a link , they show a button is it? Adding a bunch of crap into email body is worth that?
This is right out of Microsoft's embrace/extend playbook.
1. I book a flight, and get a flight confirmation email from the airline. It includes a machine-readable version of my flight info in the metadata.
2. I press a button, and the flight gets added to Google Calendar, or a flight-status tracking app, or a shared travel calendar service for people who fly a lot. Note that this stuff doesn't need to be written by Google; it's an open format.
