Sticky notes with visibility control

I'd love some kind of sticky note token which would be a simple box with text inside. I'd also love to be able to control who could see the note. Right now I'm setting up some boxes with text on the GM overlay, which is a great way to put my notes right where it is easy to see them, but moving them around and editing the text is a pain. Extra nice would be the ability to color the background/foreground of the note and tweak its transparency.

This would be a nice feature so you could annotate a lot of the stuff about encounters and the like directly on the map instead of having to refer back to other documents.