This is a nice project. Reagan Ward wanted to give people an idea of whether he and his colleagues were in the office or not. He wired up a Pi with some perfboard and some RGB LEDs, did some nifty programming in C++ and Python and hey presto visitors to their office could tell their status without walking down the corridor to find out. Admittedly, it only saves people about 8 seconds, but it’s still a cool little project. Read more here.