SatUplink Shield in Lieu of Cell Phone

With a $99 annual fee, it could be spendier than the cell-phone method, but seems to be far more robust and will work on farms outside of good cell phone coverage. You can't program it remotely, as it only talks one way, so I would think of this as a separate branch of the project. Regardless could still be super valuable.

http://www.sparkfun.com/products/11088