Request on bukkit forums, I don't plan to update this. Feel free to use the code however you wish.

BackOff/.classpath

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+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.6"/>
+	<classpathentry kind="lib" path="C:/MC Server/bukkit.jar"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>

BackOff/.project

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+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>BackOff</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

BackOff/.settings/org.eclipse.jdt.core.prefs

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+#Sat Feb 05 17:28:29 PST 2011
+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.6
+org.eclipse.jdt.core.compiler.codegen.unusedLocal=preserve
+org.eclipse.jdt.core.compiler.compliance=1.6
+org.eclipse.jdt.core.compiler.debug.lineNumber=generate
+org.eclipse.jdt.core.compiler.debug.localVariable=generate
+org.eclipse.jdt.core.compiler.debug.sourceFile=generate
+org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
+org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
+org.eclipse.jdt.core.compiler.source=1.6

BackOff/bin/plugin.yml

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+name: BackOff
+main: com.bukkit.nossr50.BackOff.BackOff
+version: 1.0

BackOff/src/com/bukkit/nossr50/BackOff/BackOff.java

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+package com.bukkit.nossr50.BackOff;
+
+import java.io.File;
+import java.util.HashMap;
+import org.bukkit.event.player.*;
+import org.bukkit.Server;
+import org.bukkit.event.Event.Priority;
+import org.bukkit.event.Event;
+import org.bukkit.plugin.PluginDescriptionFile;
+import org.bukkit.plugin.PluginLoader;
+import org.bukkit.plugin.java.JavaPlugin;
+import org.bukkit.plugin.PluginManager;
+import org.bukkit.entity.Player;
+
+/**
+ * BackOff for Bukkit
+ *
+ * @author nossr50
+ */
+public class BackOff extends JavaPlugin {
+    private final bPlayerListener playerListener = new bPlayerListener(this);
+    private final HashMap<Player, Boolean> debugees = new HashMap<Player, Boolean>();
+    private final String name = "BackOff";
+
+    public BackOff(PluginLoader pluginLoader, Server instance, PluginDescriptionFile desc, File folder, File plugin, ClassLoader cLoader) {
+        super(pluginLoader, instance, desc, folder, plugin, cLoader);
+    }
+
+    public void onEnable() {
+        PluginManager pm = getServer().getPluginManager();
+        pm.registerEvent(Event.Type.PLAYER_MOVE, playerListener, Priority.Normal, this);
+        pm.registerEvent(Event.Type.PLAYER_COMMAND, playerListener, Priority.Normal, this);
+        pm.registerEvent(Event.Type.PLAYER_CHAT, playerListener, Priority.Normal, this);
+        PluginDescriptionFile pdfFile = this.getDescription();
+        System.out.println( pdfFile.getName() + " version " + pdfFile.getVersion() + " is enabled!" );
+    }
+    public void onDisable() {
+        System.out.println("BackOff disabled.");
+    }
+}
+

BackOff/src/com/bukkit/nossr50/BackOff/bPlayerListener.java

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+package com.bukkit.nossr50.BackOff;
+
+import java.util.ArrayList;
+
+import org.bukkit.Location;
+import org.bukkit.block.Block;
+import org.bukkit.entity.Player;
+import org.bukkit.event.player.PlayerChatEvent;
+import org.bukkit.event.player.PlayerEvent;
+import org.bukkit.event.player.PlayerListener;
+import org.bukkit.event.player.PlayerMoveEvent;
+
+/**
+ * Handle events for all Player related events
+ * @author nossr50
+ */
+
+
+public class bPlayerListener extends PlayerListener {
+    private final BackOff plugin;
+    
+    static ArrayList<String> backOffList = new ArrayList<String>();
+	public boolean isBackOff(String playerName) {return backOffList.contains(playerName);}
+    public void removeBackOff(String playerName) {backOffList.remove(backOffList.indexOf(playerName));}
+    public void addBackOff(String playerName) {backOffList.add(playerName);}
+    static ArrayList<String> ibackOffList = new ArrayList<String>();
+	public boolean isBackOffi(String playerName) {return ibackOffList.contains(playerName);}
+    public void removeBackOffi(String playerName) {ibackOffList.remove(backOffList.indexOf(playerName));}
+    public void addBackOffi(String playerName) {ibackOffList.add(playerName);}
+    
+    public static double getDistance(Player player1, Player player2)
+    {
+    return Math.sqrt(Math.pow(player1.getLocation().getX() - player2.getLocation().getX(), 2) + Math.pow(player1.getLocation().getY() - player2.getLocation().getY(), 2)
+    + Math.pow(player1.getLocation().getZ() - player2.getLocation().getZ(), 2));
+    }
+    public static double getDistance(Location loc, Player player2)
+    {
+    return Math.sqrt(Math.pow(loc.getX() - player2.getLocation().getX(), 2) + Math.pow(loc.getY() - player2.getLocation().getY(), 2)
+    + Math.pow(loc.getZ() - player2.getLocation().getZ(), 2));
+    }
+
+    public bPlayerListener(BackOff instance) {
+        plugin = instance;
+    }
+    public boolean isPlayer(String playerName){
+    	for(Player herp : plugin.getServer().getOnlinePlayers()){
+    		if(herp.getName().toLowerCase().equals(playerName.toLowerCase())){
+    			return true;
+    		}
+    	}
+    		return false;
+    }
+    public Player getPlayer(String playerName){
+    	for(Player herp : plugin.getServer().getOnlinePlayers()){
+    		if(herp.getName().toLowerCase().equals(playerName.toLowerCase())){
+    			return herp;
+    		}
+    	}
+    	return null;
+    }
+    public void onPlayerMove(PlayerMoveEvent event) {
+    	Player player = event.getPlayer();
+    	Location to = event.getTo();
+    	Location from = event.getFrom();
+    	for (Player derp : plugin.getServer().getOnlinePlayers()){
+    		if(isBackOff(derp.getName()) && !isBackOffi(player.getName())){
+    			if(player != derp && (getDistance(player, derp) < 7)){
+    			if(getDistance(to, derp) > getDistance(from, derp)){
+    				player.teleportTo(event.getFrom());
+    				}
+    			}
+    		}
+    	}    
+    }
+    public void onPlayerCommand(PlayerChatEvent event){
+    	String[] split = event.getMessage().split(" ");
+    	Player player = event.getPlayer();
+    	if(player.isOp() && split[0].equalsIgnoreCase("/backoff")){
+    		if(split.length == 1){
+    			if(isBackOff(player.getName())){
+    				removeBackOff(player.getName());
+    				player.sendMessage("Back off mode disabled");
+    				return;
+    			} else{
+    				addBackOff(player.getName());
+    				player.sendMessage("Back off mode enabled");
+    				return;
+    			}
+    		}
+    		if(isPlayer(split[1])){
+    			Player target = getPlayer(split[1]);
+    			if(isBackOffi(target.getName())){
+    				removeBackOffi(target.getName());
+    				target.sendMessage("Removed from back off mode immunity");
+    				if(!target.getName().equals(player.getName()))
+    				player.sendMessage("Removed " + target.getName() + " from back off mode");
+    			} else {
+    				addBackOffi(target.getName());
+    				target.sendMessage("Added to back off mode immunity");
+    				if(!target.getName().equals(player.getName()))
+    				player.sendMessage("Added " + target.getName() + " from back off mode");
+    			}
+    		}
+    	}
+    }
+}
+

BackOff/src/plugin.yml

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+name: BackOff
+main: com.bukkit.nossr50.BackOff.BackOff
+version: 1.0