I'm looking for standards surrounding the diagramming of application
interfaces, specifically game interfaces. I am not interested in
standards that diagram screen layout, but rather those that precisely
specify the flow or storyboarding of all screens or states in the
game. Ideally, the standard would include interaction-specific diagram
elements:

  * What event triggered the transition to a new screen, including
conditional triggers (only if data x=y) or system-initiated triggers
(30 seconds have gone by, or the controller has been removed from the
console).

  * Distinguishing events or flows when more than one user is
controlling the UI simultaneously. (2 players on a console)

  * Distinguishing different elements of the UI. Showing a message
dialog on the same screen, switching to a new screen, or updating the
contents of data on the current screen should all be diagrammed
differently.

My current research has turned up:
  * UML's Activity Diagrams, Interaction Overview Diagrams, and State
Machine Diagrams
    - These seem ill-suited to interface diagramming (but if they are
used by a particular industry for this, it would be good to know).

  * The UMLi standard
    - Only one editor that I've found, targetted to per-screen designs
and use-case based actor/process UML modelling.

  * The UIML standard
    - This is an XML-based text standard with no diagram uses.

  * The BPMN standard
    - The best candidate I've found, but it's not targetted to UI
design. Specifically, it's describes "processes" instead of screens.
I've been unable to find references of industries or groups suggesting
its use for UI flowcharting.

A great answer would describe a standard in use by an industry
specifically for designing game UI screen flow, with graphical tools
that support it.

A good answer would include a list of standards not described above
that are related, and/or examples of where the above standards are in
use for diagramming UI flow.