Captain's Log is a small LDB feed that stores the messages you receive over the various communications channels (whisper, party, guild, raid, battle.net, etc.). Currently 10 messages are stored per medium, and these are displayed in the tooltip you receive when mousing over the plugin on your LDB display.
This addon requires a LDB display addon in order to be displayed.
Right now I don't have many more plans for this as I'm quite happy with where its ended up.