I never used them, so maybe I'm wrong, but aren't they just things you put in front of an existing regular phone camera (for example 24mm on the new Iphone) and then they just take a picture with a 24mm opening, but looking through whatever 120mm telephoto objective you stacked on top, without it having an effect on the photo quality?
In other words, if a 24mm opening can let a certain amount of light and information to the sensor, do the telephoto lenses change that somehow or is it literaly as if you pointed the phone through a binocular, since whatever passes through the telephoto then has to filter further through the standard 24mm lens?