Evaluation of Bluetooth Hands-Free profile for sensors applications in smartphone platforms

Nowadays, the wide diffusion of smartphones has completely changed the interaction of people with the surroundings. In fact these devices are equipped with a large number of sensors, like GPS receiver, 3-axis accelerator, which can enrich the user experience, collecting data from the external environment. Moreover, additional sensors can be used to enlarge the set of data providing information usually not available in a smartphone, like biomedical data. Usually, Bluetooth is used to connect external sensors to smartphone. Several commercial solutions are already available on the market. Unfortunately, different types of smartphone require the use of dedicated external sensors, due to the different Bluetooth data profile supported by the different Operative System (iOS, Android). In this paper the Bluetooth Hands-Free profile has been evaluated to transmit sensor information to smartphone, since it is the only profile supported both by Android as well as iOS devices. A prototype of a photoplethysmographic sensor with Hands-Free interface has been realized and interfaced to commercial smartphone, showing the feasibility of this approach.