heat cable..... well, i like it, but not for frogs. it is very good to place under the tank for snakes, as you can zigzag ( with duck tape or even better electrical tape) it the way you want, it is excellent for incubators or styrofoam box while traveling. I bet it should be excellent to heat up roaches bins too, but for frogs not so much, it works well when placed in the enclosure, but you can't use it inside because you need to duck tape it and tape inside is a VERY bad idea, especially for frogs. you can place it outside as well with tape, but it will look awful and you will be mostly heating the air around the tank, but not inside, well inside too, but not much. hm... unless you tape it high up so a frog can't reach it... but you better be sure, if ducktape (any tape) is stick to a snake, it is possible to take it out, but if the same happens to a frog, the only way to take it out is with a skin. that is why I'm saying it is a very bad idea.
i was trying different ways to save up on electricity, with many cages you kinda need to think about it cables are good for that, heat mats too, but I'm sticking up with mostly lamps for frogs, alternatively for a few cages i have heat mats on a sides ( and heat cable for my BRB) going full time and as additional source red lamps plugged into hydrotherm, this way the usage of red lamp is less.

don't try to make same tamp everywhere in the cage, they need to have gradient and will choose where they want to be, colder or warmer side.

you can plug multiple heat sources into hydrotherm.