What is a privacy friendly application that you'd love to have, but no one has developed yet?

Sms isn't secure or private, it doesn't make sense to include it in a privacy focused messaging app.

I also would like to have a universal messaging client but sadly it doesn't seem possible , just look at the recent reverse engineered iMessage apps, why would you waste all that effort reverse-engineering proprietary chat apps, when they can get (and will get) shut down by the service. Especially while better, open protocols exist.