diff --git a/package.json b/package.json
index ed0e2d185..0308aa6f7 100644
--- a/package.json
+++ b/package.json
@@ -40,9 +40,9 @@
     "lodash.defaultsdeep": "4.6.0",
     "minilog": "3.1.0",
     "promise": "7.1.1",
-    "scratch-audio": "latest",
-    "scratch-blocks": "latest",
-    "scratch-render": "latest",
+    "scratch-audio": "^0.1.0-prerelease.0",
+    "scratch-blocks": "^0.1.0-prerelease.0",
+    "scratch-render": "^0.1.0-prerelease.0",
     "scratch-storage": "^0.1.0",
     "script-loader": "0.7.0",
     "stats.js": "^0.17.0",
diff --git a/src/engine/blocks.js b/src/engine/blocks.js
index 0c90d1a64..9e4a4c9ed 100644
--- a/src/engine/blocks.js
+++ b/src/engine/blocks.js
@@ -194,7 +194,7 @@ class Blocks {
         // UI event: clicked scripts toggle in the runtime.
         if (e.element === 'stackclick') {
             if (optRuntime) {
-                optRuntime.toggleScript(e.blockId);
+                optRuntime.toggleScript(e.blockId, {showVisualReport: true});
             }
             return;
         }
@@ -273,16 +273,22 @@ class Blocks {
      */
     changeBlock (args) {
         // Validate
-        if (args.element !== 'field' && args.element !== 'mutation') return;
+        if (['field', 'mutation', 'checkbox'].indexOf(args.element) === -1) return;
         const block = this._blocks[args.id];
         if (typeof block === 'undefined') return;
 
-        if (args.element === 'field') {
+        switch (args.element) {
+        case 'field':
             // Update block value
             if (!block.fields[args.name]) return;
             block.fields[args.name].value = args.value;
-        } else if (args.element === 'mutation') {
+            break;
+        case 'mutation':
             block.mutation = mutationAdapter(args.value);
+            break;
+        case 'checkbox':
+            block.isMonitored = args.value;
+            break;
         }
     }
 
@@ -342,6 +348,20 @@ class Blocks {
         }
     }
 
+    
+    /**
+     * Block management: run all blocks.
+     * @param {!object} runtime Runtime to run all blocks in.
+     */
+    runAllMonitored (runtime) {
+        Object.keys(this._blocks).forEach(blockId => {
+            if (this.getBlock(blockId).isMonitored) {
+                // @todo handle specific targets (e.g. apple x position)
+                runtime.toggleScript(blockId);
+            }
+        });
+    }
+
     /**
      * Block management: delete blocks and their associated scripts.
      * @param {!object} e Blockly delete event to be processed.
diff --git a/src/engine/execute.js b/src/engine/execute.js
index 707859551..2b66c5e73 100644
--- a/src/engine/execute.js
+++ b/src/engine/execute.js
@@ -85,7 +85,7 @@ const execute = function (sequencer, thread) {
         } else {
             // In a non-hat, report the value visually if necessary if
             // at the top of the thread stack.
-            if (typeof resolvedValue !== 'undefined' && thread.atStackTop()) {
+            if (typeof resolvedValue !== 'undefined' && thread.showVisualReport && thread.atStackTop()) {
                 runtime.visualReport(currentBlockId, resolvedValue);
             }
             // Finished any yields.
diff --git a/src/engine/runtime.js b/src/engine/runtime.js
index f57a0e9f9..34c008a1e 100644
--- a/src/engine/runtime.js
+++ b/src/engine/runtime.js
@@ -52,6 +52,13 @@ class Runtime extends EventEmitter {
          */
         this.flyoutBlocks = new Blocks();
 
+        /**
+         * Storage container for monitor blocks.
+         * These will execute on a target maybe
+         * @type {!Blocks}
+         */
+        this.monitorBlocks = new Blocks();
+
         /**
          * Currently known editing target for the VM.
          * @type {?Target}
@@ -362,11 +369,13 @@ class Runtime extends EventEmitter {
      * Create a thread and push it to the list of threads.
      * @param {!string} id ID of block that starts the stack.
      * @param {!Target} target Target to run thread on.
+     * @param {?boolean} optShowVisualReport true if the script should show speech bubble for its value
      * @return {!Thread} The newly created thread.
      */
-    _pushThread (id, target) {
+    _pushThread (id, target, optShowVisualReport) {
         const thread = new Thread(id);
         thread.target = target;
+        thread.showVisualReport = optShowVisualReport;
         thread.pushStack(id);
         this.threads.push(thread);
         return thread;
@@ -416,8 +425,11 @@ class Runtime extends EventEmitter {
     /**
      * Toggle a script.
      * @param {!string} topBlockId ID of block that starts the script.
+     * @param {?object} opts optional arguments to toggle script
+     * @param {?string} opts.target target ID for target to run script on. If not supplied, uses editing target.
+     * @param {?boolean} opts.showVisualReport true if the speech bubble should pop up on the block, false if not.
      */
-    toggleScript (topBlockId) {
+    toggleScript (topBlockId, opts) {
         // Remove any existing thread.
         for (let i = 0; i < this.threads.length; i++) {
             if (this.threads[i].topBlock === topBlockId) {
@@ -426,7 +438,10 @@ class Runtime extends EventEmitter {
             }
         }
         // Otherwise add it.
-        this._pushThread(topBlockId, this._editingTarget);
+        this._pushThread(
+            topBlockId,
+            opts && opts.target ? opts.target : this._editingTarget,
+            opts ? opts.showVisualReport : false);
     }
 
     /**
@@ -632,6 +647,7 @@ class Runtime extends EventEmitter {
             }
         }
         this.redrawRequested = false;
+        this._pushMonitors();
         const doneThreads = this.sequencer.stepThreads();
         this._updateGlows(doneThreads);
         this._setThreadCount(this.threads.length + doneThreads.length);
@@ -641,6 +657,13 @@ class Runtime extends EventEmitter {
         }
     }
 
+    /**
+     * Queue monitor blocks to sequencer to be run.
+     */
+    _pushMonitors () {
+        this.monitorBlocks.runAllMonitored(this);
+    }
+
     /**
      * Set the current editing target known by the runtime.
      * @param {!Target} editingTarget New editing target.
diff --git a/src/engine/target.js b/src/engine/target.js
index d72937f65..c4f690aa9 100644
--- a/src/engine/target.js
+++ b/src/engine/target.js
@@ -20,7 +20,7 @@ class Target extends EventEmitter {
         super();
 
         if (!blocks) {
-            blocks = new Blocks(this);
+            blocks = new Blocks();
         }
         /**
          * A unique ID for this target.
diff --git a/src/playground/playground.js b/src/playground/playground.js
index fe06b4144..c1b655a58 100644
--- a/src/playground/playground.js
+++ b/src/playground/playground.js
@@ -92,6 +92,7 @@ window.onload = function () {
     workspace.addChangeListener(vm.blockListener);
     const flyoutWorkspace = workspace.getFlyout().getWorkspace();
     flyoutWorkspace.addChangeListener(vm.flyoutBlockListener);
+    flyoutWorkspace.addChangeListener(vm.monitorBlockListener);
 
     // Create FPS counter.
     const stats = new window.Stats();
diff --git a/src/sprites/rendered-target.js b/src/sprites/rendered-target.js
index 694d78612..1ffc00a1e 100644
--- a/src/sprites/rendered-target.js
+++ b/src/sprites/rendered-target.js
@@ -696,6 +696,7 @@ class RenderedTarget extends Target {
         newClone.effects = JSON.parse(JSON.stringify(this.effects));
         newClone.variables = JSON.parse(JSON.stringify(this.variables));
         newClone.lists = JSON.parse(JSON.stringify(this.lists));
+        newClone._customState = JSON.parse(JSON.stringify(this._customState));
         newClone.initDrawable();
         newClone.updateAllDrawableProperties();
         // Place behind the current target.
diff --git a/src/virtual-machine.js b/src/virtual-machine.js
index f85caf4b7..719bf6cc7 100644
--- a/src/virtual-machine.js
+++ b/src/virtual-machine.js
@@ -59,6 +59,7 @@ class VirtualMachine extends EventEmitter {
 
         this.blockListener = this.blockListener.bind(this);
         this.flyoutBlockListener = this.flyoutBlockListener.bind(this);
+        this.monitorBlockListener = this.monitorBlockListener.bind(this);
     }
 
     /**
@@ -413,6 +414,18 @@ class VirtualMachine extends EventEmitter {
         this.runtime.flyoutBlocks.blocklyListen(e, this.runtime);
     }
 
+    /**
+     * Handle a Blockly event for the flyout to be passed to the monitor container.
+     * @param {!Blockly.Event} e Any Blockly event.
+     */
+    monitorBlockListener (e) {
+        // Filter events by type, since monitor blocks only need to listen to these events.
+        // Monitor blocks shouldn't be destroyed when flyout blocks are deleted.
+        if (['create', 'change'].indexOf(e.type) !== -1) {
+            this.runtime.monitorBlocks.blocklyListen(e, this.runtime);
+        }
+    }
+
     /**
      * Set an editing target. An editor UI can use this function to switch
      * between editing different targets, sprites, etc.