There are many implementations of DIY cell phones based on Arduino and Raspberry Pi, so if you want something different than market can offer, you can start working on tour own version. Tyler lately introduced pretty slim version of RasPi phone called tyfone. Here raspberry Pi interfaces FONA – cellular module and 3.5” touch LCD display. Feature list extends with RTC and 5MP camera which enables taking HD photos.
Raspberry Pi interfaces LCD module via SPI interface so, there are plenty of GPIO left for other periphery. FONA talks to Raspberry Pi via UART. Since Pi is a Linux driven board it easily houses other standard interfaces like WiFi. By default it comes with USB, and other RasPi interfaces. Typhone is powered with 1200mah LiPo battery which can be charged from USB. 5V boost circuit ensures right voltage to power the phone. Phone software runs a custom python soft called TYOS which gives easy way to make calls, display info like battery level, time, cell connection status, send SMS, etc.