You can use any language you like to develop apps for Glass: Python, PHP, Ruby, Java…

the apps will [initially] be hosted in the cloud, via the Google Mirror API, utilizing RESTful web services. Scroll past the video for basics.

video: Sarah Price in a Google Developer Video alongside Glass developers Timothy Jordan and Jenny Murphy, released on Jan 15, 2013.

Additional detail:

ANY language can output / parse REST requests, which are sent and received via standard http protocol, just like an address in a web browser.

Some basics are:

• To create a resource on the server, use POST.
• To retrieve a resource, use GET.
• To change the state of a resource or to update it, use PUT.
• To remove or delete a resource, use DELETE.

Your cloud-based app will simply need to respond to the appropriate calls.

Typically, you will both send and receive data in packages, wrapped in contextual cues. The three primary packaging formats for REST services are:

• JSON
• XML
• XHTML

A good place to start learning about REST is here:

• Learn REST: A Tutorial