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.)
I just hope Web Intents makes it into the actual release - and in a way that is usable by normal users. Seems to me this should be a priority, instead of putting all that effort into yet another single sign-on fantasy.
If this happens as part of a large integrated experience as you promised that's fine, but I fear that you are taking on too much, going for a complex and over-engineered package that may never be ready or actually usable, instead of concentrating on this one single important thing which really needs to get done.
I used to share your skepticism about single sign-on. I'm actually quite bullish about BrowserID because it uses concepts that both users and websites are very familiar with (email, 'validated email addresses'), and works it in a flow that feels very much like facebook connect. It's really neat rather than overengineered IMO (and I can say that because I didn't do any of the engineering ;-).
Similarly, the apps project is a lot about recognizing what mobile apps did well, and filling in the gaps in the web (stores, receipts, APIs) that will make it possible for people to translate their mobile appdev skills into the broader web.
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.)