Also currently the engine stops running when it goes in to the background to save CPU and battery, so it would probably only be able to alert when you're already looking at it.
Can we prevent this somehow? Especially with the new multiplayer features, it seems that the game will go wildly out of sync if you switch to another tab. This applies even in the desktop, I think, where the game goes to 1fps in the background.
Can you imagine if league of legends booted you if you alt-tabbed? Ugh.