Heating Cables are used when building a vivarium type of enclosure and can buried directly into the substrates themselves. As mentioned earlier they are also used in rack systems. Heat cables are often capable of being wrapped around branches, plants, etc. I have rarely seen these actually used in any collections and this is because lighting elements and their respective reflectors can be hidden by a canopy placed on top of the enclosure.
Radiant heat panels AKA pig blankets are another option for those attempting to heat a large enclosure such as a Monitor or tortoise enclosure. They are usually placed on an enclosure wall in order to radiate heat outward into the ambient air but I have seen them placed on the floors of large enclosures and then covered with substrate. Radiant heat panels come in a variety of sizes and are made of rubber molded around the actual heating element itself.
Now you have an overview of heating elements currently available for heating your reptile, amphibian, and insect pets. While the final choice is up to you, I personally recommend and use the Ceramic Heating Element type of heater. For larger enclosures the radiant heat panels would be a more efficient choice.