The kind of app I'm looking for is pretty specific. So please read the whole paragraph before answering.
The idea is to have a "tunnel", or a pipe, between two users. We are talking about a Windows or Mac client, presented as a "drop zone" on the edge of the screen, hiding automatically. As soon as I drag & drop a file, link, text or whatever i want in there, the element is sent to the friend. He receives a pop up telling him about the element, and can open it just by clicking on that pop up. Again, the idea is a really private sharing, with a simple and efficient UI.
Please don't tell me DropBox is what I'm looking for : no drop zone, files stack up in the shared folder, doesn't allow to open the elements right away...
The closest software to that I've ever found is Droplr, which upload anything you drop on the icon, and put the link in the clipboard. The thing is that it's too annoying to have each time to open the chat window and paste the link, and same thing on the other side for my friend.
Do any of you think about something like that ? Or should I code it myself ?