This is boring, and sure some available (can't be bothered to look), but at work, wear an earpiece for the 'phone ..of course, not the ones that go over your head, would wreck me hair ..
Nobody ever knows whether you are having a conversation with a customer or not, and embarassing when you speak to them during a conversation whilst they are listening.. they have to signal to you, with peculiar finger movements, that they are on-line. Sure there must be some headphones somewhere that light up red when you are actually on line.