Cheapest Solution for wireless freezer monitoring?

[tortillasoup]

I've got a freezer in another house that is unoccupied and I need to keep tabs on it to be notified if and when the unit fails. I was thinking a hybrid android/bluetoot/wireless setup where an old smartphone would wirelessly send an update if there is an issue with a temperature probe inside of the freezer. Is there an already created solution that is/does this that isn't too expensive?

 

[Red Squirrel]

Arduino or raspbery pi with a ds18b20 sensor. May need to write a script on a PC to interface serialy with it and take action such as send email. RPI would omit the need for separate PC. While your at it can add ac fail sensor by hooking a relay to a wall wart. Power goes out relay switches position.