Bartender does even more than that, you can make certain icons reappear in the menu bar when they change for a certain period to make you aware of them.

And combined with iStat menus I even make for instance my battery-icon hide whenever docked and fully charged.

Also, quite some icons such as the WiFi, Volume, Bluetooth are only visible at all times in my case because I need a quick and easy way to alter the settings or be aware of them. This problem can be solved for me by automating these settings by profiles or my location such as School/home/on-the-move. This can be achieved by apps such as ControlPlane (http://www.controlplaneapp.com), you can even dimm your screen, kill apps that need a network connection to work such as Dropbox/Droplr/Twitter...

Very similar to what Llama (https://play.google.com/store/apps/details?id=com.kebab.Llam...) does on my Android phone.