docs: function(successCallback, errorCallback, options) {
          argscheck.checkArgs('fFO', 'accelerometer.watchAcceleration', arguments);
          // Default interval (10 sec)
          var frequency = (options && options.frequency && typeof options.frequency == 'number') ? options.frequency : 10000;
  
          // Keep reference to watch id, and report accel readings as often as defined in frequency
          var id = utils.createUUID();
  
          var p = createCallbackPair(function(){}, function(e) {
              removeListeners(p);
              errorCallback && errorCallback(e);
          });
          listeners.push(p);
  
          timers[id] = {
              timer:window.setInterval(function() {
                  if (accel) {
                      successCallback(accel);
                  }
              }, frequency),
              listeners:p
          };
  
          if (running) {
              // If we're already running then immediately invoke the success callback
              // but only if we have retrieved a value, sample code does not check for null ...
              if (accel) {
                  successCallback(accel);
              }
          } else {
              start();
          }
  
          return id;
      }