Thanks. I can simply create an app, that checks every hour all new posts on hive and crosscheck their author name is active on steemit / blurt. which this step i have not gone yet but would be a possible solution to see who is still active on those 2 other platforms. This will end up in a Page, that just shows Authors on HIVE beeing active on other 2 platforms. It's easy to do - just throw api calls around and display the data.