I've used EZ-Bridge LT devices to send a signal 4-500' feet and it's worked flawlessly with very strong signal and no flakiness. More expensive than the devices noted above, but at $230 it includes both sides of the bridge, and each can act as a wifi access point.
As with many FOSS projects, my focus is on creating it and wrangling bugs. What little documentation exists is quite old and starting to be somewhat incorrect. I did just post a screencast on how to update a crop plan from one season to the next. I would welcome more contributions of documentation and/or screencasts. Be in touch if you're interested in helping; I would love it!
As of 1/23/14, the link is dead. Anyone have an updated one? I'm all for open source and DIY, but I also like simple and working. The cost of the parts for Rover is comparable to this device. Very interesting.
While the software is designed for electric fences, the 120v switch could power anything. Code would have to be changed, of course, but it wouldn't be a huge undertaking for someone interested in doing so.
The system, as it currently exists, relies on the cellphone + cellphone library to determine if the power has failed/been turned off. If it detects that, it automatically sends a text that the "fence is down". This was conceived of as a secondary feature, with the primary feature being the ability to dis-able the fence from afar. There is no current capability to test the charge on the fence, which seems like what you would need to see if a battery/solar powered fence is not working. The Arduino could run off of solar, though, so it's not impossible.
I write and maintain the Crop Planning Software (http://cropplanning.googlecode.com/ and http://www.farmhack.net/tools/crop-planning-software) project and have put together a "labor and materials" budget module for it. Still in development, but I wonder if you might be interested in working together to test that/these? CPS works around the idea that you enter info for HOW you grow crops once, then enter info about WHEN and HOW MUCH you need to grow for separately. Right now the module is working in that you can enter data (tasks and time & materials needed for each) once for each crop and it automatically generates a "labor and materials budget" for the whole crop plan. What do you think?
I'm curious to know what parts of the software (http://farmhack.net/tools/crop-planning-software) don't fit your farm and how I could make the software more flexible or useful. All feedback is welcome!
I bought the TI level shifter you linked to at AdaFruit and wired it up as directed but couldn't get it to work ... until I realized that the diagrams you have on the "Building on the Shield" page refer to a different shifter with a different pin count and layout. I went back and rewired it according to the instructions on the AdaFruit page and the datasheet and got it to work.
It's a little more complicated then you've drawn up, but here's what I ended up with:
Connect 3.3V to shifter pins 1 and 20.
Connect/link shifter pins 10 and 19.
Arduino GND and cell phone GND to shifter pin 10.
Arduino pin 6 to shifter pin 2.
Arduino pin 5 to cell phone Rx.
Shifter pin 18 to cell phone Tx.
Also, not sure it's pertinent or not, but the phone I bought had some old texts left on it and the GSMSerial example would NOT work (spit out bogus info) until I cleared them all. As soon as I did, though, it started working perfectly.