Unless your room is very cold (60-65 degrees) you shouldnt need to heat it. Usually the lights heat the vivarium 5-10 degrees above room temperature (depending on the distance from lights to vivarium).
Using a ceramic heater on or near a enclosed glass vivarium sounds very uncontrollable and dangerous unless used with a thermostat inside the viv. Much easier to just heat the room up a bit with a plug in heater.
The ceramic bulbs get way to hot for use with dart frogs imo. I live in Minnesota and my frog basement this last winter regularly stayed around 68 and everybody did just fine. If i were going to use anything to heat an individual viv it would be one of the smallest heatmats made but even then i would be useing a proportional thermostat. As stated above a small plug in heater for the room is the best solution
They get too hot! I once had a 75w heat emitter on my first herp tank, it cracked and overheated the viv. I was wondering about my new 20l vert viv, I managed to get 3 13-20w bulbs on top, and the glass has yet to crack.