OMG CSS LEDs!!!
I don't know if it's really necessary to provide a lot of preamble for this entry. Recently I needed indicators. I decided to go with some semi-skeumorphic LEDs and you can see the result in this handily embedded codepen:
[ See the Pen djhAt by F. Stephen Kirschbaum (@fskirschbaum) on CodePen. ]
I may revisit this one later to expand a little, but I think this should all be pretty self explanatory.