The use of wireless ECG body sensors in two pilot studies is presented. The first study, running at the Department of Cardiovascular Surgery of the University Medical Centre Ljubljana, is focused on the investigation of postoperative atrial fibrillation. The patients are monitored with wireless ECG body sensors one day before and five days after the surgery. The second study has been established at the primary care level in the Community Health Centre Ljubljana, with the intention to establish heart rhythm screening. As both studies are still in progress, we present just their setup and some interesting findings that emerged in their starting phase. Based on evidences from long-term ECG measurements, we identify several still open ECG research questions that could utilize the vast amount of long ECG recordings obtained from the pilot studies.