The continuous monitoring of patients' vital parameters during recovery, essential in critical situations, is usually performed by dedicated supervision equipments and specialized personnel. For non-critical situations, to reduce the hospitalization and personnel expenses, patient rehabilitation can take place at home, supported by portable devices for vital parameter monitoring. Usually, such devices are storing-only systems, thus a periodic data downloading and off-line analysis must be performed by the specialized medic. Moreover, the high price of these portable monitoring systems does not allow an exclusive allocation of the device for long time to each patient. In the optic of the recent growth of in-home assistance field, nowadays there is a significant interest in the development of compact, low-power and low-cost systems for the continuous monitoring of health conditions as a support for the normal life of elderly or fragile population. Smartphone based-systems are very promising for such kind of use, due to the decrease of terminal prices, increase in computational resources and data storage capacity, availability of various sensors and standard communication interfaces, easiness or configurability for different purposes, intuitive user interface by means of touch screen and other multimedia equipments and so on. The present work describes the development and the realization of a single-lead electrocardiogram trace acquisition system, based on and powered by a smartphone device. It offers easiness of application on the patient under examination and high storage capacity. Thanks to the possibility of easily developing and installing software utilities, different strategies of data processing and communication could be implemented, thus allowing new scenarios in the in-home assistance field to be effectively explored.