Essentially, what this app seems to be is a webkit browser + notifications in a tabbed interface. You connect different communication service accounts to it -- like Gmail, Slack, HipChat, Intercom, Freshdesk -- and then each service is logged into the web page version of the service in a tab in Manageyum.
I'm trying to figure out how this would be much different than simply opening each of these websites in a tab in my web browser, other than it includes notifications for new messages. I think that makes the usefulness less, and in the end, I prefer the app functionality over the browser interface.