gmusicbrowser

To update gajim's status with your currently playing song, open gmusicbrowser's settings, navigate to the plugins tab, and make sure now playing is enabled.

As command, enter

gajim-remote change_status online %a-%t

Or whatever you want to submit. Note, if you want to use spaces between artist and title for example, you'll have to use single quotes, like this:

gajim-remote change_status online '%a - %t'

For the development version of gmusicbrowser, there's also an option to run a command when music stops. You'd want to enter something like this there:

gajim-remote change_status online