[neilv]

I had a similar awkwardness when I tried to have a non-audio indicator for something when laptop screen was off.

When I was using my carrying my laptop around public places in town most of the day, before I'd close the laptop lid (which triggered an immediate suspend at some low level), I'd press a hotkey to "secure" the laptop. This locked the screen and started a process to zero various RAM caches, and scrub misc. temp/junk files. (Not that I needed that, but I was figuring out privacy&security at the time.) To indicate to me that it was OK to close the lid and leave, instead of doing a beep that might bother someone in a library or something, I flashed an LED for an instant. The LED available was the white ThinkLight at the top of the LCD, which was bright enough to illuminate the keyboard and nearby workspace.

You might guess how this could appear in a library. Sudden flash, as if from a cameraphone, in someone's peripheral vision, coming from the direction of a guy who is suddenly leaving.

So I disabled that indicator, because it seemed infinitely more risky and harmful than the threat of a spy neutralizing me and using advanced computer forensics on my laptop to recover a fragment of a high-value spam email.