The film was probably done in late 80's/early 90's. Don't know if it's a TV movie or not. A boy around 10 years old is sent by his mum to go stay with his dad and his girlfriend(or wife) for a while. Strange things start happening with the electrical devices. There is a house across the street where the guy apparently went crazy. The girlfriend almost drowns when she is in the shower. At the end the dad is cutting down a telephone pole outside his house when he realizes the house is possessed by the electronics. The dad and son are in a the back of a police car laughing then it's finished.

Pulse (http://www.imdb.com/title/tt0095924/)