Attached patch add support for indicator applets on lxpanel (disable by default). This patch add a lxpanel plugin which can show indicators when there are installed.
Indicator applets are described on https://wiki.ubuntu.com/DesktopExperienceTeam/ApplicationIndicators. This patch is based on version 0.3.8 of indicator applet (https://code.launchpad.net/~indicator-applet-developers/indicator-applet/applet-0-3).
You need to provide some pointers to applications that already use this feature so it can be thoroughly checked out.
I claim this is not the design you would ultimately want, where your new implementation is a separate applet.
The existing "tray" applet should be extended to be the Host and should mix icons from Xembed clients and from Indicator clients. Although I have not done a thorough analysis of it, it seems the panel should also be the Watcher so there is not a separate daemon to do that. Over time there could be fewer Xembed clients and more Indicator clients.
I do not want to ship this and get "indicator" instances into people's configuration files and then have a hard time getting them back out.