This Bukkit plugin prevents a common cause of "ghost blocks" (blocks that a client thinks have been mined yet the server knows are still there). This most often happens when a player is mining blocks very quickly while occasionally falling.
When all of the following conditions are met:
- A player is breaking a block
- That player is not flying (creative flight)
- That player is not standing on solid ground
then this plugin will send an update to the client so that it knows the correct state of the block.