The Digger's Diary is a unique feature of the Wii U version of Shovel Knight that is integrated with the Miiverse. Players choose an avatar and then can write or draw posts through the tablet. Posts are bound to the rooms they were written in, allowing players to communicate about challenges and secrets in the area.
See Also Edit
http://yachtclubgames.com/2014/06/diggers-diary-detailed/ for the design process behind the Digger's Diary.