Patients without clinical knowledge must be able to use mobile electrocardiography (ECG) devices to collect healthcare data outside a clinical setting safely and effectively. We conducted a simulated use test to assess usability from a patient perspective, with 18 ECRI employee volunteers who were familiar with smartphones, but unfamiliar with the two devices being evaluated. The largest a priori concerns were how long it would take to collect a valid ECG reading and how easy it was to share data captured by the devices. Overall the systems (ECG device plus smartphone app) were rated similarly in terms of usability, and none took so much longer than the others that it could be considered less useful. However, the testing did reveal some significant usability problems with each system. Moreover, it is unclear how the data produced by these devices, which needs to be reviewed by a clinical expert, will impact communication between patients and providers. More research is needed to understand how having patients use medical devices with smartphone apps could impact the workflow and communications of the primary care or specialty physicians to whom the data produced by these devices will be sent.