Mozilla is contributing to the Web Intents standardization and implementation effort, and in fact Mozilla's Open Web Apps project and Web Intents are being designed to work together and to benefit each other greatly (just as BrowserID and Open Web Apps are being designed to benefit each other).

To be more concrete: When a web page uses an intent like "upload a photo", Firefox will check to see if any of your "apps" support that intent. For example, if Flickr has an OWA app and you have already installed it, then Firefox will instantly ask if you want to choose one of your Flickr photos to upload. If you click an intent that the browser doesn't already have a handler for, it can offer to install an app from the web to handle the intent.

Open Web Apps is part of the infrastructure to turn Web Intents from a low-level API into a complete user experience. And BrowserID is also part of that integrated experience. (In the full vision for BrowserID where the browser manages your identities, you can do things like install an app and be "logged in" instantly without creating an account or typing a password.)