One thing that critics of the movie got wrong (probably because they didn't watch the movie again in a while) is why didn't they call the police or call Kevin to go to a neighbor's place.
The reason is all there in the movie. A tree fell over and knocked over the phone cables, killing the phone connection. Also they DID call the police, but the police in this movie are highly inept jackasses who don't even realize that a string of burglaries is happening in the neighborhood by the Wet Bandits. They do send a cop over, who just knocks on the door for a bit and then leaves. Kevin does hear the knocking, but he is scared and hides beneath his bed. When the cops doesn't get a response, he doesn't bother further.
But yes, cell phones would change everything.