I do not know if anyone offered this or not, but I think it would be a good idea to set up this so people who want an extra privacy of their balance would be able to enable this function via the settings.
I love this app and I think what Revolut is doing is fantastic. But every time I tell my friends about this app and want to show how it works, I kind of have to hide the balance as it is my bank balance after all. Same goes when I open the app in public to check what I have spent etc, anyone would be able to see the balance.
Make a functionality so once you open the app, the main balance is blurred and you will be able to check or see if once you hold it with your finger on the blurred part to expose the text and once you release it gets blurred again.
I hope this idea or similar functionality will be implemented very soon.