Capacitive Soil Sensor
Just got one of these and it uses some really clever design features - an ISP header can be added to open it up for normal programming.
I love how they used an LED as a light/dark sensor and the way they measure parasitic capacitance is just delightful! Details here.
I've been meaning to pick up some of these soil sensors, I've read a bit about them and apparently the capacitive ones are far superior to the more common resistive ones.
I like this idea and have been considering doing something on these soil sensors for a while.
Disclaimer - I have whatever is the opposite of a "green thumb", plants shriek and die whenever I'm in the room with them and I believe I'm one of the few human beings who has ever killed a plastic plant! So the presentation would have to be theoretical, as no plant would be able to withstand being watered by me!
P.S. Your attachment seems to be a Kindle preview of some sort, but I'm unable to read it.
"Never trust a computer you can’t throw out a window." — Steve Wozniak