07-31-2013 03:51 PM - edited 07-31-2013 03:53 PM
You can write an application that would get invoked for a certain type of stream/protocol/etc. but invoking the native Media Player from the Email application is outside of application development. That is purely based on the functionality implemented in the Media Player to be compatible; as a developer external to both applications, you can't directly affect their behaviour in this way.
Edit: Take a look at the invocation framework documentation to see how you can invoke an application as a handler for content: