I did a research to find why skype only show in the system tray and not as an indicator. It seems it needs the sni-qt 32 bit package.
I'll have to do some research on this. I don't know how multilib/multiarch works in Arch yet, but we will need a 32-on-64 bit version of qt4-ubuntu and sni-qt.
I know this is an ancient issue so I apologise for the necrobumping but if anyone else encounters this issue you can solve it by install sni-qt and then appending 'Skype' to the list contained in com.canonical.Unity.Panel systray-whitelist using dconf-editor.