Several projects based on Smart-phone systems have been proposed in different fields and many more application scenarios are being explored. A critical aspect still unresolved is the possibility of acquiring external information, such as data from other Sensors. Sensor interface is therefore possible if a suitable front-end able to digitize Sensor data and to handle the communication with the Smartphone is employed. In order to lower the complexity and the cost of the front-end as well as to reduce its power consumption, an effective method for the acquisition of external sensor signals through the Smartphone audio input is proposed in this paper. A sensor system composed by a photoplethysmographic sensor for Cardiac signal monitoring and a pair of electrodes for tissue impedance estimation has been used. Specific software routines for Android operating system have been developed to process the acquired Sensor signals providing Visualization, Data storage and simple Data analysis, and thus demonstrating the feasibility of the proposed approach. © 2015 Elsevier B.V., All rights reserved.