Query: How do you 'invite' contacts on WP8?

I know you can add contacts in the Peoples hub and enter details manually, but is this the same as inviting a contact via the old style Live Messenger and waiting for them to accept the invite?

Basically, I want to be able to see whether that contact is online in Messages or Skype on Windows Phone. I'm not sure if just adding a contact in Peoples automatically adds them as a 'friend'.

If invites are required, how do you do this on Windows Phone?