Having made a very basic shild for this project using a stripboard, I realised the potential for manufacturing a proper shield. I hope that this one will for the basis of a balancing robot (like my first attempt) but hopefully more complete.
Its main purpose is to jiggle the pins around into useful positions, so I can directly plug in two servos, an L298-based dual H bridge motor driver, a Bluetooth trasceiver and an accelerometer/gyro.
There are also a couple of LEDs for debugging, a pair of (hopefully useful) buttons and a potential divider with centre tap to an analog input which I can use to monitor main battery voltage.
The board is printed and etched using a time-honoured system seen here.
The board has no external power supply, and I can hear you worrying for me. No need. The Arduino's 5V regulator is perfectly happy driving two micro servos with no load (twiddling a couple of ultrasound rangers is no load).