To the OP, there are many ways to heat a cage, which one is best for you depends greatly on the air temperature/humidity levels in the room that the cage is in. Heat mats and flexwatt are basically the same thing. Bith MUST be regulated by a thermostat and carefully monitored by a thermometer to be used safely. heat lamps (I prefer infrared heat lamps) can also be very dangerous is used improperly.
For more info check out this thread I wrote on cage heating: http://ball-pythons.net/forums/showt...t-Thermometers
And just to make sure that everything else is right I strongly suggest that you check out this thread: http://ball-pythons.net/forums/showt...ius)-Caresheet