A wearable ambulatory data recorder that senses physiological parameters of a patient, and stores physiological parameter data for later retrieval, as well as techniques for using such a wearable ambulatory data recorder, are described. The data recorder includes one or more sensors located on or within a housing. The data recorder may include an adhesive layer for attachment to a patient. In some embodiments, the housing may be within a patch, e.g., bandage, which includes the adhesive layer. The housing may be waterproof. Features of the data recorder such as size, waterproofness, and inclusion of an adhesive may allow the data recorder to be unobtrusively worn by a patient during a variety of daily activities. The data recorder may be for single use and thereafter disposable.