I wrote a small bash application that allows me to control the music streamed from my phone to my PC via bluetooth, and I would like to know how to add a Rhythmbox like widget in Unity panel's volume control for my application.
You have to create a MPRIS DBUS interface same as any other player.
MPRIS D-Bus Interface Specification
Some thing else related to the sound indicator, your app should have an .desktop to be identified by the indicator.
