Update description of SensorLogger on website

website/index.html

@@ -14,7 +14,8 @@
      <div class="app">
       <a href="SensorLogger.apk" class="qr"><img src="SensorLogger.png" alt="SensorLogger.apk QR code"></a>
       <h2>Sensor logger</h2>
-      <p>Logs changes in accelerometer readings and allows them to be uploaded for use in research.</p>
+      <p>Logs changes in accelerometer and magnetic readings and allows them to be uploaded for use in research.</p>
+      <p>When the "start" button is pressed, the application will log sensor data for approximately 50 seconds, and then automatically upload it along with the user-supplied activity description.</p>
      </div>
     </div>
     <div id="footer"/>