Basic pH measurement using the Netduino.
Phidget have a
pH sensor and a version for the Netduino would be fun.
pH is nice and easy to measure, so it should be fairly simple. The ADC on the Netduino should be good enough for 0.1pH resolution and with 6 inputs it could do 3 probes with temperature as well.
I'd like to see a USB connected version where the host PC application does the display and measurement. Variations could include POE ethernet powered version or a Zigbee or Bluetooth connected versions.