http://bukkit.fr/index.php?threads/9676/

Offsetters.java

package fr.neatmonster.offsetters;

import java.util.Arrays;

import org.bukkit.ChatColor;
import org.bukkit.block.Block;
import org.bukkit.block.BlockFace;
import org.bukkit.event.EventHandler;
import org.bukkit.event.EventPriority;
import org.bukkit.event.Listener;
import org.bukkit.event.block.Action;
import org.bukkit.event.block.BlockRedstoneEvent;
import org.bukkit.event.player.PlayerInteractEvent;
import org.bukkit.material.Diode;
import org.bukkit.metadata.FixedMetadataValue;
import org.bukkit.plugin.java.JavaPlugin;

public class Offsetters extends JavaPlugin implements Listener {

    @Override
    public void onEnable() {
        getServer().getPluginManager().registerEvents(this, this);
    }

    @EventHandler
    public void onPlayerInteract(final PlayerInteractEvent event) {
        if (event.getAction() == Action.RIGHT_CLICK_BLOCK
                && event.getClickedBlock().getState().getData() instanceof Diode) {
            final Diode diode = (Diode) event.getClickedBlock().getState().getData();
            if (diode.getDelay() == 4) {
                final boolean offset = event.getClickedBlock().hasMetadata("offset") ? event
                        .getClickedBlock().getMetadata("offset").get(0).asBoolean() : false;
                event.getClickedBlock()
                        .setMetadata("offset", new FixedMetadataValue(this, !offset));
                event.getPlayer().sendMessage(
                        ChatColor.YELLOW + (offset ? "Exiting" : "Entering") + " offset mode.");
            }
        }
    }

    @EventHandler(priority = EventPriority.MONITOR)
    public void onBlockRedstone(final BlockRedstoneEvent event) {
        for (BlockFace face : Arrays.asList(new BlockFace[] { BlockFace.NORTH, BlockFace.SOUTH,
                BlockFace.EAST, BlockFace.WEST })) {
            final Block block = event.getBlock().getLocation()
                    .add(face.getModX(), face.getModY(), face.getModZ()).getBlock();
            if (block.getState().getData() instanceof Diode) {
                final Diode diode = (Diode) block.getState().getData();
                if (face.getOppositeFace() == diode.getFacing() && block.hasMetadata("offset")
                        && block.getMetadata("offset").get(0).asBoolean()) {
                    final Block input = block.getLocation()
                            .add(face.getModX(), face.getModY(), face.getModZ()).getBlock();
                    event.setNewCurrent((int) input.getData() + diode.getDelay());
                }
            }
        }
    }
}

plugin.yml

name: Offsetters
version: 1.0
author: NeatMonster
main: fr.neatmonster.offsetters.Offsetters