This Open Source DIY Cellphone might not be the latest and greatest Samsung phone but it is something that you can build yourself. It is Arduino based and all of the details can be found here.
Via: Electronics Lab and Arduino Blog
“The DIY Cellphone is a working (albeit basic) cellphone that you can make yourself. It can make and receive phone calls and text messages, store names and phone numbers, and display the time. It builds on the hardware and software in the Arduino GSM Shield but extends it with a full interface, including display, buttons, speaker, microphone, etc.”