this is my entry for Sir_Craftypants' Ultimate Treehouse Building Contest
features a working clock that displays the actual gametime!
there is also a hot air balloon, which can be controlled by stepping on the pressure plate in the basket. It goes in the direction you're looking, and moves pretty fast. Can go north, south, east, west, up and down. It also checks for air in that direction before moving, so it wont overwrite any blocks.