ZeroPhone is an open-source smartphone that can be assembled for 50$ in parts. It is Linux-powered, with UI software written in Python, allowing it it to be easily modifiable - and it doesn't prohibit you from changing the way it works.
Making cheap open-source smartphones more widespread
Having a smartphone that respects your privacy
Having a smartphone that can be customized
Strengthening open-source software ecosystem
Educating people about how smartphones work
Power-user and programmer-friendly
Independent and respecting your privacy
Open-source hardware and software
Modular and extensible; based on Raspberry Pi Zero
Built from available components, can be assembled independently
Currently, ZeroPhone is based on Raspberry Pi Zero, SIM800L GSM modem and 1.3« OLED screen and button interface. The hardware is almost ready for ZeroPhone v1.0, and now software is being developed to have a basic set of phone functions.