Sadly, there is no easy built-in solution to do this yet.

However, you can follow the same procedure as duplicating an app within the same system (which can now be achieved through the UI), but you don't have to change any guids, because the app will be unique already on your other agent. A problem though is that objects used in your app might not exist on your destination agent. A similar question was recently posted about that topic.

Note that this will take a duplicate, not sharing the original app. So changes in one agent will not be reflected on the other agent. Unless they are in a DMS of course, where apps are synched between all agents.