At Kyso [1] we let you do this (I'm one of the founders) - you can run Jupyterlab online and start servers inside Jupyterlab that you can share with the world (Jupyterlab will run on instance-id.cloud.kyso.io).

You can install viola and then just run it on port 8000 from within the jupyterlab terminal and you can share the url with anyone (it will be instance-id-8000.cloud.kyso.io)

We're actually thinking of supporting Viola natively in the next few weeks, what kind of app do you want to run?

[1] https://kyso.io