At a developer conference for Project Ara, Googles upcoming modular smartphone platform, executives showed off a prototype build-it-yourself handset and described a roadmap for future plans. While the prototype the company showed wasnt working due to unfinished code, its hardware appeared to be in good condition.During the demonstration, project head Paul Eremenko easily slid out a Wi-Fi module from the prototype and attached a pulse oximeter that measures your blood oxygen level. With Project Ara devices, youll be able to swap out anything from batteries and cameras to displays and processors without using any tools .