Homeowners insurance is named perils on contents. That means, in order for the item to be covered the cause of the damage has to be specifically listed in the policy.
Examples of named perils include: fire, lighting, wind storm. So, if the phone was on your coffee table and your house burned down...then the homeowners policy would cover it.
If your phone fell out of your pocket and broke...there is no peril in the homeowners policy that covers this - therefore, your phone would not be covered.
Usually the insurance purchased from the cell phone provider provides more coverage than your homeowners policy would pay.