My attention was brought to a process named
indicator-application-service because it was idling at 28% CPU usage. What does this program do?
indicator-application-service is the service that is used to manage application indicators. Application indicators are a way for applications that don't provide any indicator integration with any of the existing indicators such as Messaging, Session, DateTime, etc. You can think of it as the replacement for the former systray.
Applications that want to provide status that doesn't fit into the existing categories can register with indicator-application-service and get an icon displayed in the panel.
Read here: https://launchpad.net/indicator-applet
The indicator applet exposes Ayatana Indicators in the Gnome Panel. Ayatana Indicators are an initiative by Canonical to provide crisp and clean system and application status indication. They take the form of an icon and associated menu, displayed (usually) in the desktop panel. Existing indicators include the Message Menu, Battery Menu and Sound menu.