Franz is a free messaging app/former emperor of Austria, that combines chat & messaging services into one application.

Franz – a free messaging app for Slack, Facebook Messenger, Whatsapp, Telegram and more

The app itself is based on electron. It acts as a browser.It will be super easy if you have a web app.

James Cheuk

Wonder how hard / reliable it would be to do some integrations

Yes, it works well. It allows me to multiple slack accounts at the same time. And I can turn on and off services quickly.

@James Cheuk does it work well?  How do you like it?

This, with combined identities and one inbox instead of tabs on the side.