This is cool idea, but honestly i don't expect to receive call if i run LN node.
Maybe not now, but it's not hard to imagine LN node operators communicating like this, also we are slowly moving towards dystopian future and censoring stuff will be more and more common,
it is happening even now for some people, just a matter of time when it will affect you or someone you know.
That is why Impervious is working on this cool idea of using Bitcoin network and Lightning Network for building something that is resistant to censorship and surveillance.
Fair point, but honestly i doubt Redphone will be common option since the user need to have Bitcoin and run LN node. IMO other application or protocol such as Signal and Matrix are more practical.