I've tried to use jumpapplet under both gnome3 (gnome-shell) and ldxe but in each case I don't see an icon appear anywhere.
no config file
I think gnome3 uses a different protocol for displaying applets. I don't know about lxde. So the part that displays the icon would need to be rewritten. If anyone wants to work on this, I can try to merge it later.
Closed as won't fix. GNOME shell incompatibility is mentioned in documentation.