Lock your desktop, mute music or run any other command when leaving your PC. There are dozens of apps like this. This one just aims to make it beautiful, modern and easy.

Blueproximity was a program to do this, but it never worked great for me, and has since rottened. This project was inspired, but I trid making it Gnome-ish. That means simple, limited options, but does the job.

Argos is a free GNOME version of BitBar. Both lets you run any script to create an icon in the panel (or Mac OS X Menu Bar). You can see lots of plugins here: BitBar plugins.

This screenshot shows the hosts file, opened from the argos extension. The extension is shown as a notebook icon with the number of unknown entries.

It complains on forgotten entries in your /etc/hosts file. See Argos-hosts for more info.