If it's urgent, you can borrow a friend's cellphone, that's true. But, wait, crap, now you need to notify everyone that needs to get a hold of you of your new

If it's urgent, you can borrow a friend's cellphone, that's true. But, wait, crap, now you need to notify everyone that needs to get a hold of you of your new number, which we've already established is something we want to avoid. If only there was a service that let you configure which physical device your calls were being routed to...