use an h-bridge with a temperature sensor attached for monitoring
an h-bridge will allow you to turn it either hot or cold (reverse polarity) using 2 pins
Its the same type of component that allows forward and reverse on a motor only no protection diodes are needed since its not an inductive load.
Here is an example for a motor using only 2 pins (I would use a couple more transistors to make sure both couldnt be in the on state at the same time as that would likely cause smokehttp://www.bobblick.com/techref/projects/hbridge/hbridge.html
or a possibly more effecient design using MOSFETS here http://www.cadvision.com/blanchas/hexfet/np-s.pdf