Then, I started to think to myself about the long history of such actions on analog lines. Example: you need to call your relative to tell her there was a fire at your house. Your relative- who, presumably doesn't have call waiting- is talking to her friend. You get a busy. Then you ask the operator to interrupt this call, and to ask your friend to hang up because an emergency call is coming in.
But what about when either the caller, recipient (or both) has VoIP? Not every VoIP service offers call waiting. And even if you do have call waiting on your VoIP, line, how are you going to interrupt your intended recipient's call if they don't have call waiting? I mean, I don't think there are Skype or Vonage operators that can do this, right?
If your recipient is on a softphone, you could try to send them an email. But because email programs can be set at various frequencies, it isn't a sure bet your recipient will notice your "please get off the phone" email even if you assign High Priority to your message.
So how can you interrupt a VoIP call- or interrupt an analog phone user from your VoIP?
I may be missing something here- but don't you think I have a point?