The ZeroPhone is based on the raspberry pi. https://hackaday.io/project/19035-zerophone-a-raspberry-pi-smartphone/log/51839-project-description-and-frequently-

The ZeroPhone is based on the raspberry pi. https://hackaday.io/project/19035-zerophone-a-raspberry-pi-smartphone/log/51839-project-description-and-frequently-asked-questions https://hackaday.io/project/19035-zerophone-a-raspberry-pi-s... Reddit AMA: https://www.reddit.com/r/raspberry_pi/comments/5nwmfx/im_making_a_pipowered_opensource_mobile_phone/ https://www.reddit.com/r/raspberry_pi/comments/5nwmfx/im_mak... $50. Calling, SMS. Alarm clock, calendar, calculator, phonebook, file browser, web browser and music player. I expect these will be very simple given the screen.