This module plugs right onto the GPIO connector of your Raspberry Pi, and provides it with a 20x4 character display, 6 pushbuttons, a temperature sensor, and an analog input. A version with a built-in real-time clock is also available, so that your Pi always knows the exact time, internet acces or not.
The LCD, buttons, temperature sensor, analog input, and RTC can be accessed over a SPI or I2C interface.
This board also breaks out the two SPI busses, I2C bus, and UART, so connecting more of our expansion boards is still an option.
If you order the board with a RTC mounted, it will come including the required CD2032 coin cell.

Specifications:
20 characters by 4 lines white-on-blue LCD
6 pushbuttons
MCP9700 temperature sensor
1 analog input
Optional:
MCP794xx battery backed-up real-time clock (or compatible)
The RTC is always I2C because that is easier with the Linux device drivers.

Raspberry Pi and cables not included

Links:

Case for the Raspberry Pi with 20x4 RPi UI of the current version (V2.1) or the old version (V2.0)

Datasheets:
Documentation for the complete PCB