A few months ago, I wrote about my reverse engineering attempt to Logitech Unifying devices. Back then, I concluded my post with big hopes on the future after receiving a document with some part of the specification of the HID++ 2.0 from Logitech.
A couple of weeks ago, some of my summer work has been merged to UPower, adding battery support for some Logitech devices.
I still don't know why but many GTK+ applications use something called eggtrayicon. As far as I know, eggtrayicon.c is a file written in 2002 by Anders Carlsson which implements the Freedesktop.org system tray procotol for GTK+ applications.