Let me see.....standing water....electrical appliance....my bare butt....
....pass.....
You're just fine with electric water heaters, people use electric heaters for aquariums all the time...
All they have to do is make sure the resistive elements are well sealed. Given the size of a toilet seat and that it runs off of 12V, the website specifies 'sealed', at only 12 watts at that.
I'll pass, too. This sounds like a solution to a non-problem.
Says somebody who's never had to use an outhouse in the wintertime, or even get up at night when dad liked to keep the house around a nice toasty 50F.
Sure, us Manly Men don't need it, but Mom wasn't too happy...