I get what you mean now. But honestly why can't you just pause the game.. I mean if we're talking about a game here then why can't you just hit esc then that pauses the game. When you come back into the game and hit resume it just resumes. I don't see why that can't just be a work around?
I wasn't able to open your example because you saved it on the newest beta (I'm on the r216 still), but I understand what you're saying. I have sort of a specific use case that I'm not expecting Scirra to support, but I was really just hoping there would be a solution I could use already available.
My game will be playable on a large touchscreen table in my local public library. Users can open games from the Windows 8 Metro screen, at which point they go full screen. If a user presses the Windows button and returns to the Metro menu to pick another game, the library does not want my game to continue to produce sound while running in the background. So, the ideal solution in my use case would be an auto-suspend, as I can't expect the users (mostly small children) to press a pause button before abandoning my game.
Now that I'm thinking about it, I wonder if exporting the game as a proper Windows 8 app might behave differently. I hadn't thought about it until this point because I wasn't planning on putting the game in the Windows Store, but it might be worth testing out.