No icon on the statusbar
If you can't find Echofon icon on Firefox's status bar, please check following things:
On Firefox 4, you need to enable "Add-on bar" first (View -> Toolbars -> Add-on Bar)
If you have a lots of add-ons in your Firefox, Echofon might conflict with the other extension. Please try to disable all of them and enable only Echofon.