I created Scone to teach myself Objective-C. It used the brand new Rendezvous technology to find other copies of itself running on the same network. When you sent a message to another machine in Scone it would appear as a new note in the Stickies app. I wouldn’t return to Objective-C until 9 years later when I made Last Time.
You can still find Scone on MacUpdate. It’s a whopping 83KB download.