Back up a level...do you really want to pay someone to watch the other person you paid to clean the house? Why not just hire a reliable cleaner that can work without supervision?
I think the challenge I see is "wife" when really you're talking about general services. TaskRabbit already address the service sector and you can hire someone to perform a number of tasks to help you manage your life.
On the upside, prostitution is a huge industry which equates to a large total addressable market.
I think such a thing would require a large adoption to work, but the use cases are too bizarre and already have work arounds. For your example, why not a friend, family member, or neighbour?