Version 1 was based on a PIC and was designed with Royan Ong:
here you can see the first prototype. The gumstix sits on top and there are a lot of headers for accessing the I/O and providing switchable power.
The back of the board has most of the components.
The PIC provides A/D together with some adjustable external amplifiers, also digital I/O. Commands sent to the PIC via the I2C bus control the power to external units and fetch readings etc.
The MSP430 based version was produced in volume in autumn 2007, with refinements by Robert Spanton:
Here the top view shows the same principle with the gumstix and break-out pins for GPIO/ADC/etc. The bottom view shows the tunable amplifiers, backup batteryand MSP430. This version has host usb and can power-down the gumstix completely - only using 6 microamps in sleep. The idea is that the microcontroller runs data sampling but boots the ARM when a communications/control period is scheduled. As the ARM runs Linux it can run control scripts in Python, tcp/ip networking etc.
This shows a prototype from summer08 boxed to allow space for a battery, test temp/hum and multicolour LED.
This is the configuration of the LCD-based gumstix (designed to be powered on 100%), with Wifi, verdex, host USB (can run web browser for easy touch-screen interfaces)
This is the configuration deployed on the glacier in Iceland - an extra I/O board plugs in underneath the gumsense and provides easy push-in I/O, programming header, and debug LEDs. This uses a GPRS modem, drives a dGPS and runs from batteries with solar/wind power.