It is in fact wifi switcher as nicolai noted. I use this particular gadget often, as there are some times I do not want to auto-switch to wifi. The widget is often good about remembering it's last status across reboots, but not always. That could explain it coming and going...

I just had to reboot (Recaller crashed for some reason), and Wifi switcher didn't remember its off status. SSH Status, on the other hand, always remembers the its state.