There is already a patented disposable corn plastic strainer, but it is the divoted kind, rather than a flat mesh sheet that lays across the sink. (since 2010)
There is already an enzyme drain cleaner (since 1966), but I would want to have people use this on a regular basis, like shower spray, after each use or daily. I'm not sure if that makes it different enough.
There is totally a drain shaver already! That is so cool!
There is thankfully not a patent on a drain monster. There is a vermiculture compost bin, however.
There are flat screens as drain protectors, but it would be easy to alter one (a la the coffee cozies), to become patentable.
I didn't find a patented mesh drain ball.
I didn't find personified drain covers.
I didn't find a drain mill.
Wow, I am surprised that there are patents on so many of these! I like your idea of a mesh drain ball but I am wondering how easy it would be to clean? Maybe if it was two hemi spheres that attached to each other and could be taken apart for cleaning all the hair and gunk. Did you do a google search on the patented products? Because they might be patented but not really in the market- an opportunity pour vous.
I did google searches on the patented products... I agree that there is market potential. I also appreciate your use of French.