Photos by Eliot Weisberg/ReadWriteWeb. Creative Commons licensed.

Sergey Brin took the stage at the end of the keynote to do a surprise demo of Google’s Project Glass. He warned that the demo “could go wrong in about 500 different ways,” but then he turned to the screen to reveal his friend JT flying overhead about to jump out of an airplane.

JT was coming in live via Google+ Hangout over the prototype glasses. Brin and JT had a surprisingly natural conversation, with JT up in an airplane and Brin on stage at Moscone.

After riling up the crowd, the skydivers got Moscone in their sights. “Hellooooo, San Francisco!” they shouted as they leaned out of the open door, and then they jumped from the plane. The Hangout video was perfect. As the skydivers plummeted toward the ground, the video streamed in live. See for yourself:

It was as exhilarating to watch the demo go off perfectly as it must have been for the skydivers, who glided to safety on the roof of Moscone as we all watched breathlessly.

The devices used in the demo were prototype Project Glass glasses with a touchpad on the side, a microphone and small speakers, and they had a gyroscope, accelerometers and a compass for location awareness.

Brin announced the Google Glass Explorer Edition at the end of the keynote. It’s available for preorder exclusively at I/O, only for U.S.-based attendees due to regulatory obstacles. It will be sold for $1,500 and will be available “early next year.”

Updated September 11, 2013 with embedded video of the stunt.