All of the software support will be updated over time.
For external sensors or other external modules, there will be guidelines published to develop your project. For I2C, initial functionality will be to have you directly pass I2C commands from the Android level code to the external connector. More functionality will be added later.
At the moment we're really working hard to make sure the platform is as robust as possible for production.
We're looking at BT 4.0 for the fall release, but we're currently hung up on how to handle iphone support because we're stuck in limbo with Apple's MFI approval department. Our final bluetooth solution somewhat hinges on the feedback from Apple, as they have some special requirements.
Our current design is difficult to open/close, but we're looking at modifying the housing design next month to allow this.
The metal we're using now is aluminum. It can be anodized any color. BUT, we're considering going to a stainless steel instead. Everything is Aluminum these days.