I have two suggestions. First, you could somehow have streaming video and music files. There could be a way to set the files to only appear as icons/shortcuts and when activating them stream them to the second computer. In the long run there could be a built in conversion tool, on the fly converting and streaming, in case one of the pcs has a slow internet connection and needs a lower bitrate. Second, we should be able to add and remove secrets in connected computers. You could be using the program itself to sync the settings of two pcs, in case there is no way to show the folders the secondary computer has it could have a temporary folder in which the files would be uploaded and when the location is finalized it could move them there. Surely both of these are hard since it would probably need a common database of usernames to make sure two computers should be synced and the first one is something still far away from the current goals of the syncapp. It could however use google/facebook/twitter/whatever accounts for the second feature and the first one has seen many implementations you could draw experience from. --edited for better formatting--
