Palpitations (noticeable pounding, fluttering or irregular heart beat) and pre syncope (near blackout) are common ED problems sometimes due to an abnormal heart rhythm. Diagnosis is difficult as examination and electrocardiogram (ECG) are commonly normal and symptoms have usually resolved by the time the patient arrives in the ED. Diagnosing an abnormal heart rhythm as the cause of symptoms rests on capturing it on an ECG and patients are usually advised to return to the ED for a 12-lead ECG should symptoms recur. The investigators will recruit 242 participants aged 16 years or over presenting to the ED or Medical Assessment Unit of the Royal Infirmary of Edinburgh with an episode of palpitations or pre-syncope and who remain undiagnosed after ED assessment. The investigators will randomise and allocate participants to either study or control arms. All study arm participants will be given an AliveCor Heart Monitor and trained in the use of the device. Control arm participants will receive standard care only. If a participant allocated to the study arm has palpitations or pre-syncope during the 90-day study period, the participant can record an ECG using the AliveCor Monitor which can be viewed by the study team. Participants will be asked to log symptoms and whether the participant was able to record an ECG during the symptoms in a participant symptom diary, which the participant will return to the research team along with the Participant satisfaction and compliance questionnaire, and smart phone based event recorder at the end of the 90 days in a pre-paid stamped, addressed envelope. Participants will be phoned at 90 days to remind the participant to complete the Participant satisfaction and compliance questionnaire and to return this with the symptom diary and smart phone based event recorder. The investigators believe a smart phone based event recorder will allow better and earlier diagnosis in patients.