Adds a "World Anchor" (not a Railcraft reference at all!) block that forces chunks to stay loaded even if there is no player nearby. Plants will keep growing and redstone mechanisms will continue working while you are away.
It has two operation modes: 3x3 and 5x5 chunks.
To toggle between modes, use Right Click on the block.
Press F3 + G to see chunk grid.
May be demanding on your PC's performance if used extensively.