A family purchases a home robot designed to look like a grandmum. Their neighbours immediately buy a more expensivve model as the two families always try to up the other one. Both grandmums start to "terorize" their families because they were set up to ensure the mums exercise, the kids study etc. Apart from that they start causing problems to the other family ... cut ropes with hanging clothes, pierced tires, etc. Once they get to killing each other family's pets the parents get really worried about the safety of their kids. The grannys later destroy each other while fighting and the families decide that they'll be better off without any robots. (It's some time since I saw this so the details may be off.) Mainly thanks to the design of the robots it's rather a comedy than a horror. Unless you are ten. And a rather good comedy!
CS