The iHealth Track blood pressure monitor has a function for detection of irregular heartbeats. When this is the case, an irregular heartbeat icon 
appears to the left of the pulse rate value.
Note - When an irregular heartbeat is detected, measurement of blood pressure may be inaccurate. A new measurement is recommended.
In theory this should not cause for concern, but if the icon starts to appear more frequently (for example, several times a week for daily measurements) or suddenly appears more often than usual, we recommend that you report it to your doctor, who can perform further tests.
This feature does not in any way replace a cardiological examination but helps to detect an irregular heartbeat at an early stage.
*credit to Sylvain of iHealth Labs EU