Having a good worth ethic is respectable. However, working smart can be as effective as working hard. Still, lying about doing work is unethical in my opinion, even if it's clever. Depending on the situation though, I think that letting your employer know that a job can be automated may lead to better opportunities in the future... maybe?
I remember that someone was considering making a program to automate a co-workers job, since it was just simple data entry. They never actually did it though.