Get a cheap drinks fridge, and modify the existing thermostat to regulate to the desired maximum temperature, or get a thermostatic mains switch to control power to the fridge, it only operates when the temperature is higher than usual.
E.g.
RS | Process Control | Sensors and Transducers | Temperature Sensors | Thermal Switches This closes when the temperature reaches 50 Celsius. The contacts are rated for 250Vac at up to 8A.
It sounds like you enjoy making things work through computers. So how about these?:
http://thermometer.co.uk/903-usb-the...ure-stick.html
2 Channel Relay Module - Devantech - USB-RLY02 - Proto-PIC.co.uk - UK Suppliers of Electonics - Robotics - SparkFun - LilyPad - Arduino