diff --git a/ble/services/ImmediateAlertService.h b/ble/services/ImmediateAlertService.h
new file mode 100644
index 0000000..6073adc
--- /dev/null
+++ b/ble/services/ImmediateAlertService.h
@@ -0,0 +1,94 @@
+/*
+ * ImmediateAlertService.h
+ *
+ *  Created on: 2016-02-02
+ *      Author: KUANG Qi
+ */
+
+#ifndef __BLE_IMMEDIATE_ALERT_SERVICE_H__
+#define __BLE_IMMEDIATE_ALERT_SERVICE_H__
+
+#include "ble/BLE.h"
+
+class ImmediateAlertService
+{
+public:
+    enum AlertLevel_t
+    {
+        NO_ALERT = 0,
+        MILD_ALERT = 1,
+        HIGH_ALERT = 2
+    };
+
+    typedef void (*callback_t)(AlertLevel_t level);
+
+    /**
+     * @param[ref] ble
+     *               BLE object for the underlying controller.
+     */
+    ImmediateAlertService(BLE &bleIn, callback_t callbackIn,
+            AlertLevel_t levelIn = NO_ALERT) :
+            ble(bleIn), alertLevel(levelIn), callback(callbackIn), alertLevelChar(
+                    GattCharacteristic::UUID_ALERT_LEVEL_CHAR,
+                    reinterpret_cast<uint8_t *>(&alertLevel), 1, 1,
+                    GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_WRITE_WITHOUT_RESPONSE)
+    {
+        static bool serviceAdded = false; /* We should only ever add one Immdiate Alert service. */
+        if (serviceAdded)
+        {
+            return;
+        }
+
+        GattCharacteristic *charTable[] =
+        { &alertLevelChar };
+        GattService immediateAlertService(
+                GattService::UUID_IMMEDIATE_ALERT_SERVICE, charTable,
+                sizeof(charTable) / sizeof(GattCharacteristic *));
+        ble.gattServer().addService(immediateAlertService);
+        serviceAdded = true;
+
+        ble.gattServer().onDataWritten(this,
+                &ImmediateAlertService::onDataWritten);
+    }
+
+    /**
+     * Update the callback.
+     */
+    void setCallback(callback_t newCallback)
+    {
+        callback = newCallback;
+    }
+
+    /**
+     * Update alertness level.
+     */
+    void setAlertLevel(AlertLevel_t newLevel)
+    {
+        alertLevel = newLevel;
+    }
+
+protected:
+    /**
+     * This callback allows receiving updates to the AlertLevel characteristic.
+     *
+     * @param[in] params
+     *     Information about the characterisitc being updated.
+     */
+    virtual void onDataWritten(const GattWriteCallbackParams *params)
+    {
+        if (params->handle == alertLevelChar.getValueHandle())
+        {
+            alertLevel = *reinterpret_cast<const AlertLevel_t *>(params->data);
+            callback(alertLevel);
+        }
+    }
+
+protected:
+    BLE &ble;
+    AlertLevel_t alertLevel;
+    callback_t callback;
+    GattCharacteristic alertLevelChar;
+
+};
+
+#endif /* __BLE_IMMEDIATE_ALERT_SERVICE_H__ */