There are a lot of large gel masks of various sorts available on the market. I would say that what sets thermoeyes apart is that the gelpacks are small and cover just the eye area. Both with hot and cold compresses, there are plenty of people who don't want something that is going to cover the whole upper part of their face, either because of sensitive skin, facial rosacea, etc. I agree with Indrep about the XR size Thermoeyes. They are super comfy and hold heat/cold longer than the smaller ones.
Other than gel packs like the one you linked to, and the Thermoeyes product line, the other category of heat packs is things like flax or rice bags. Those are good at retaining heat/cold for quite awhile and tend to be super comfy but not everyone likes having that much weight on their eyes, and they're not quite as hygienic as sealed gelpacks.
The Dry Eye Zone