diff --git a/libs/microbit/control.cpp b/libs/microbit/control.cpp
index 2d8cc1f5..051c512a 100644
--- a/libs/microbit/control.cpp
+++ b/libs/microbit/control.cpp
@@ -159,7 +159,7 @@ namespace control {
     /**
      * Gets a friendly name for the device derived from the its serial number
      */
-    //% blockId="control_device_name" block="device name" weight=10
+    //% blockId="control_device_name" block="device name" weight=10 blockGap=8
     StringData* deviceName() {
         return ManagedString(microbit_friendly_name()).leakData();        
     }
@@ -167,7 +167,7 @@ namespace control {
     /**
     * Derive a unique, consistent serial number of this device from internal data.
     */
-    //%
+    //% blockId="control_device_serial_number" block="device serial number" weight=9
     int deviceSerialNumber() {
         return microbit_serial_number();
     }
diff --git a/libs/microbit/messages.ts b/libs/microbit/messages.ts
new file mode 100644
index 00000000..6d674823
--- /dev/null
+++ b/libs/microbit/messages.ts
@@ -0,0 +1,51 @@
+namespace messages {
+    var streamid: string;
+        
+    export function setStreamId(id: string) {
+        streamid = id;
+    }
+    
+    /**
+     * Creates a new message that includes the board serial number and the stream id if any
+     */
+    export function createMessage() : Message {
+        let m = new Message();
+        m.addNumber('board', control.deviceSerialNumber());
+        if (streamid != null && streamid.length > 0)
+            m.addString('stream', streamid);
+        return m;
+    }
+    
+    /**
+     * A message containig custom data
+     */
+    export class Message {
+        private buffer:string = '';
+        
+        /**
+         * Adds a string field to the message
+         */
+        //%
+        public addString(name:string, value:string) {
+            if (this.buffer.length > 0) this.buffer += ',';
+            this.buffer += name + ':"' + value + '"';
+        }
+        
+        /**
+         * Adds a number field to the message
+         */
+        //%
+        public addNumber(name:string, value: number) {
+            if (this.buffer.length > 0) this.buffer += ',';
+            this.buffer += name + ':' + value;            
+        }
+        
+        /**
+         * Converts the message to a JSON payload
+         */
+        //%
+        public toJSON() : string {
+            return '{' + this.buffer + '}';
+        }        
+    }
+}
\ No newline at end of file
diff --git a/libs/microbit/shims.d.ts b/libs/microbit/shims.d.ts
index 84c4ff0d..c5fb8383 100644
--- a/libs/microbit/shims.d.ts
+++ b/libs/microbit/shims.d.ts
@@ -346,13 +346,13 @@ declare namespace control {
     /**
      * Gets a friendly name for the device derived from the its serial number
      */
-    //% blockId="control_device_name" block="device name" weight=10 shim=control::deviceName
+    //% blockId="control_device_name" block="device name" weight=10 blockGap=8 shim=control::deviceName
     function deviceName(): string;
 
     /**
      * Derive a unique, consistent serial number of this device from internal data.
      */
-    //% shim=control::deviceSerialNumber
+    //% blockId="control_device_serial_number" block="device serial number" weight=9 shim=control::deviceSerialNumber
     function deviceSerialNumber(): number;
 }
 
diff --git a/sim/libmbit.ts b/sim/libmbit.ts
index 6c65f5b5..2d3979be 100644
--- a/sim/libmbit.ts
+++ b/sim/libmbit.ts
@@ -233,6 +233,13 @@ namespace pxsim.control {
             ? b.id.slice(0, 4) 
             : 'abcd';
     }
+    
+    export function deviceSerialNumber(): number {
+        let b = board();
+        return parseInt(b && b.id         
+            ? b.id.slice(1) 
+            : '42');
+    }
 
     export function onEvent(id: number, evid: number, handler: RefAction) {
         pxt.registerWithDal(id, evid, handler)
diff --git a/sim/state.ts b/sim/state.ts
index 18832f26..e639534e 100644
--- a/sim/state.ts
+++ b/sim/state.ts
@@ -511,7 +511,7 @@ namespace pxsim {
 
         constructor() {
             super()
-            this.id = "b" + Math.random().toString().slice(1);
+            this.id = "b" +Math_.random(2147483647);
             this.animationQ = new AnimationQueue(runtime);
             this.bus = new EventBus(runtime);
             this.radio = new RadioBus(runtime);