diff --git a/inc/veutil/qt/ve_qitems_mqtt.hpp b/inc/veutil/qt/ve_qitems_mqtt.hpp
index 6b62039..ee7edc0 100755
--- a/inc/veutil/qt/ve_qitems_mqtt.hpp
+++ b/inc/veutil/qt/ve_qitems_mqtt.hpp
@@ -45,6 +45,7 @@ class VeQItemMqtt : public VeQItem
 class VeQItemMqttProducer : public VeQItemProducer
 {
 	Q_OBJECT
+	Q_PROPERTY(HeartbeatState heartbeatState READ heartbeatState NOTIFY heartbeatStateChanged)
 	Q_PROPERTY(ConnectionState connectionState READ connectionState NOTIFY connectionStateChanged)
 	Q_PROPERTY(QMqttClient::ClientError error READ error NOTIFY errorChanged)
 	Q_PROPERTY(QString portalId READ portalId WRITE setPortalId NOTIFY portalIdChanged)
@@ -63,6 +64,16 @@ class VeQItemMqttProducer : public VeQItemProducer
 	};
 	Q_ENUM(ConnectionState)
 
+	// The heartbeat state tracks whether the CerboGX is actively alive
+	// and writing heartbeat timestamp updates to the MQTT broker.
+	// We might be actively connected to the VRM broker, but the actual
+	// device itself might have gone offline and so the data is "not live".
+	enum HeartbeatState {
+		HeartbeatActive,
+		HeartbeatInactive,
+	};
+	Q_ENUM(HeartbeatState)
+
 	VeQItemMqttProducer(VeQItem *root, const QString &id, const QString &clientIdPrefix, QObject *parent = nullptr);
 
 	VeQItem *createItem() override;
@@ -79,6 +90,7 @@ class VeQItemMqttProducer : public VeQItemProducer
 	void setCredentials(const QString &username, const QString &password);
 	bool publishValue(const QString &uid, const QVariant &value);
 	bool requestValue(const QString &uid);
+	HeartbeatState heartbeatState() const;
 	ConnectionState connectionState() const;
 	QMqttClient::ClientError error() const;
 
@@ -86,6 +98,7 @@ class VeQItemMqttProducer : public VeQItemProducer
 	void setPortalId(const QString &portalId);
 
 Q_SIGNALS:
+	void heartbeatStateChanged();
 	void connectionStateChanged();
 	void errorChanged();
 	void portalIdChanged();
@@ -106,11 +119,13 @@ private Q_SLOTS:
 	void doKeepAlive(bool suppressRepublish = false);
 
 private:
+	void setHeartbeatState(HeartbeatState heartbeatState);
 	void setConnectionState(ConnectionState connectionState);
 	void setError(QMqttClient::ClientError error);
 	void parseMessage(const QString &path, const QByteArray &message);
 
 	QTimer *mKeepAliveTimer;
+	QTimer *mHeartBeatTimer;
 	QTimer *mReadyStateTimer;
 	QTimer *mReadyStateFallbackTimer;
 	QMqttClient *mMqttConnection;
@@ -123,12 +138,14 @@ private Q_SLOTS:
 	QUrl mUrl;
 	QString mHostName;
 	int mPort;
+	HeartbeatState mHeartbeatState;
 	ConnectionState mConnectionState;
 	const int mReconnectAttemptIntervals[6] = { 250, 1000, 2000, 5000, 10000, 30000 };
 	quint16 mAutoReconnectAttemptCounter;
 	const quint16 mAutoReconnectMaxAttempts;
 	QMqttClient::ClientError mError;
 	QMqttClient::ProtocolVersion mProtocolVersion;
+	int mMissedHeartbeats;
 	bool mReceivedMessage;
 	bool mIsVrmBroker;
 };
diff --git a/src/qt/ve_qitems_mqtt.cpp b/src/qt/ve_qitems_mqtt.cpp
index 4eedbd4..5c5c2b1 100755
--- a/src/qt/ve_qitems_mqtt.cpp
+++ b/src/qt/ve_qitems_mqtt.cpp
@@ -68,15 +68,18 @@ VeQItemMqttProducer::VeQItemMqttProducer(
 		VeQItem *root, const QString &id, const QString &clientIdPrefix, QObject *parent)
 	: VeQItemProducer(root, id, parent),
 	  mKeepAliveTimer(new QTimer(this)),
+	  mHeartBeatTimer(new QTimer(this)),
 	  mReadyStateTimer(new QTimer(this)),
 	  mReadyStateFallbackTimer(new QTimer(this)),
 	  mMqttConnection(nullptr),
 	  mPort(0),
+	  mHeartbeatState(HeartbeatInactive),
 	  mConnectionState(Idle),
 	  mAutoReconnectAttemptCounter(0),
 	  mAutoReconnectMaxAttempts(sizeof(mReconnectAttemptIntervals)/sizeof(mReconnectAttemptIntervals[0])),
 	  mError(QMqttClient::NoError),
 	  mProtocolVersion(QMqttClient::MQTT_3_1_1),
+	  mMissedHeartbeats(0),
 	  mReceivedMessage(false),
 	  mIsVrmBroker(false)
 {
@@ -93,12 +96,28 @@ VeQItemMqttProducer::VeQItemMqttProducer(
 	const quint64 uniqueId = QRandomGenerator::global()->generate64();
 	mClientId.append(QStringLiteral("%1").arg(uniqueId, 16, 16, QLatin1Char('0')));
 
+	// start the timer once we have sent the first (empty) keepalive after subscribing.
 	mKeepAliveTimer->setInterval(1000 * 30);
 	connect(mKeepAliveTimer, &QTimer::timeout,
 		this, [this] {
 			doKeepAlive(/* suppressRepublish = */ true);
 		});
-	// start the timer once we have sent the first (empty) keepalive after subscribing.
+
+	// start the timer once we have received the first heartbeat.
+	mHeartBeatTimer->setInterval(3500); // heartbeat interval is 3s, but allow extra.
+	connect(mHeartBeatTimer, &QTimer::timeout,
+		this, [this] {
+			++mMissedHeartbeats;
+#ifdef MQTT_WEBSOCKETS_ENABLED
+			if (mWebSocket && !mWebSocket->isOpen()) {
+				qWarning() << "Missed heartbeat due to websocket disconnection";
+				onDisconnected();
+				return;
+			}
+#endif
+			qWarning() << "Missed heartbeat!  Device data is not real-time.";
+			setHeartbeatState(HeartbeatInactive);
+		});
 
 	mReadyStateTimer->setSingleShot(true);
 	mReadyStateTimer->setInterval(1000);
@@ -264,13 +283,16 @@ void VeQItemMqttProducer::onConnected()
 
 void VeQItemMqttProducer::onDisconnected()
 {
+	setHeartbeatState(HeartbeatInactive);
 	setConnectionState(Disconnected);
 	if (error() == QMqttClient::NoError
 			&& mMqttConnection
 			&& mMqttConnection->error() != QMqttClient::NoError) {
 		setError(mMqttConnection->error());
 	}
+	mMissedHeartbeats = 0;
 	mKeepAliveTimer->stop();
+	mHeartBeatTimer->stop();
 	mReadyStateTimer->stop();
 	mReceivedMessage = false;
 	if (mMqttSubscription.data()) {
@@ -377,8 +399,14 @@ void VeQItemMqttProducer::onSubscriptionMessageReceived(const QMqttMessage &mess
 	const QString notificationPrefix = QStringLiteral("N/%1").arg(mPortalId);
 	if (topicName.startsWith(notificationPrefix)) {
 		const QString keepaliveTopic = notificationPrefix + QStringLiteral("/keepalive");
+		const QString heartbeatTopic = notificationPrefix + QStringLiteral("/heartbeat");
 		if (topicName.compare(keepaliveTopic, Qt::CaseInsensitive) == 0) {
 			// ignore keepalive topic.
+		} else if (topicName.compare(heartbeatTopic, Qt::CaseInsensitive) == 0) {
+			// (re)start our heartbeat timer.
+			mHeartBeatTimer->start();
+			mMissedHeartbeats = 0;
+			setHeartbeatState(HeartbeatActive);
 		} else {
 			// we have a topic message which we need to expose via VeQItem.
 			const QString path = topicName.mid(notificationPrefix.size() + 1);
@@ -443,6 +471,19 @@ void VeQItemMqttProducer::doKeepAlive(bool suppressRepublish)
 	}
 }
 
+VeQItemMqttProducer::HeartbeatState VeQItemMqttProducer::heartbeatState() const
+{
+	return mHeartbeatState;
+}
+
+void VeQItemMqttProducer::setHeartbeatState(VeQItemMqttProducer::HeartbeatState heartbeatState)
+{
+	if (mHeartbeatState != heartbeatState) {
+		mHeartbeatState = heartbeatState;
+		Q_EMIT heartbeatStateChanged();
+	}
+}
+
 VeQItemMqttProducer::ConnectionState VeQItemMqttProducer::connectionState() const
 {
 	return mConnectionState;