I've used [EZ-Bridge LT devices](http://ez-bridge.com/) 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.
Comments
EZ-Bridge
Not so much.
Dead Link?
Simple
No solar; Yes alerts