Hi marcandre,
Blusleepproducts is connected to the family that owns Essentia (see post #5 here).
It is a type of gel foam and would be similar to the watergel made by GommaGomma here.
Elastomeric gels are a type of polyurethane and are a very durable material. It can be made as a solid gel layer, foamed, or added to other materials like polyfoam or memory foam. As you mention, it is more expensive than polyurethane or most other types of foams which is why mattresses that contain it (especially as a gel layer rather than a foam that has gel added to it) can be more expensive.
They are very safe and non toxic and have a “somewhat” viscoelastic feel but as you also mentioned it is not the same as memory foam and it also depends on whether it is “pure” or added to another material. It is a high quality material IMO.
Technogel is another example (and there are several others as well).
Phoenix