It doesn't actually show up as a service yet - follow the instructions on this page [0], see "Getting started".
Basically, create a project in API console, create an OAuth 2.0 client id, add [1] to the valid JavaScript origins and then paste your client id ({number}.apps.googleusercontent.com) into the playground [2].
Basically, create a project in API console, create an OAuth 2.0 client id, add [1] to the valid JavaScript origins and then paste your client id ({number}.apps.googleusercontent.com) into the playground [2].
[0]: https://developers.google.com/glass/playground-usage
[1]: https://mirror-api-playground.appspot.com
[2]: https://developers.google.com/glass/playground