I have a life proof case on my iPad - it's protected against water (can be submerged up to a number of metres), dust particules and drops of a relatively substantial height.
I'm fairly sure they make phone cases too.
My SIL bought one for my autistic nephew after he submerged his third iPad in the bath, which is how I found out about them.
They do have a lengthy warrenty because there are limits to their wonder - my nephew picked the case on his and the next time he threw the iPad the screen broke. They replaced the cover for free but because it had already been broken when the impact occurred they would not replace the iPad. (So make sure you regularly check it.)
Although not for children with autism, I have seen TVs enclosed in plastic containers to protect them while visiting and adolescent mental health ward.