Chroma Servo Board for Raspberry Pi is a small board that connects to a Raspberry Pi and allows you to control up to eight RC servos (or ESCs) via the serialport in the GPIO port of the Raspberry Pi. The commands for the serial version are simple ASCII. The 2x13 pin header on top is a pass through if you want to connect other cards using the GPIO-port.  The output is buffered and made 5V by a buffer IC.

If you are into AVR-programming you can reprogram the little MCU on the RPi Servo board and make the card do whatever you like. Maybe read 6 temperature sensors and send the values as ASCII on the serial port?

The card also has a 8 pin connector (unmounted) that exposes 6 GPIO-pins of the ATmega8 CPU, +3.3V and GND. With firmware version 0.2 there are experimental support to use them as as digital output controlled via a serial command. If you want to make your own firmware the pins is also the ATmega8s I2C lines (2 pins) and SPI (4 pins).

Datasheet

Schematic

Software Package

Demo Code