Experimental gardening, hydroponics, aquaponics

In December 2010 I quit a job as Instrumentation Engineer at U of A's Biosphere 2--the day before I was to have started it! I sometimes have regretted that decision (though it made it possible for me to spend another couple of weeks mud-plastering straw bale houses and helping build two domes of adobe and cob). But thankfully there's still a big world of gardening applications for electronics. And thanks to cheap microcontrollers like Arduino and their clones, and a huge variety of cheap (<$5 shipped) sensors, electronic projects for gardening are within most people's reach.

Do you have ideas for projects (electronic or not) that we could study, to determine whether they help with gardens, farms, hydroponics, or aquaponics?

On the electronics front, I have a collection of sensors and microcontroller development boards, including Arduino clones, that I am willing to lend to people and to tutor them. I'd also be interested in borrowing any peripherals you have that I don't have.

Some peripherals that I have include:

soil moisture sensor
hygrometer (humidity sensor for air)
pH meter (this one is an integrated device that could be cracked open and interfaced to Arduino)
barometer
digital thermometers
dimmers for AC lights
wireless transceivers, including Bluetooth, WiFi, and others
Ethernet boards for Arduino
battery
charger
Step-down and step-up DC-DC converters

I am interviewing local gardeners to ask their needs. Victor Ceballos told me of some things that Tierra y Libertand and Community Food Bank could use. I also plan to ask the GardenPool.org people in Mesa, who in the first year of their 480 square foot swimming pool aquaponics garden grew 75% of the food consumed by their family of five. My intention for gardens is to use the cheapest, most reliable means (often not electronic at all!) to empower people to grow as much food & medicine as possible with as little labor (time and effort) and capital (space and materials) as possible.