I believe that the telephone is revolutionary because it started a revolution of instantaneous communication.
The first models of the telephone changed culture and daily life in America and around the world from writing letters and telegrams or visiting someone in person to being able to instantly communicate with whomever at any time. The first model had a listening device and required the user to talk directly into the wall console so mobility was very limited...speaking on the phone became its own event and activity.
The mid-century rotary phone allowed people more freedom by having the listening and speaking device connected. The cord allowed more mobility by not having to stand at a fixed point at a wall, but able to move about a small radius in a room.
The first cell phone of the 1980's allowed people to go where ever they wanted to while talking on the phone. Talking on the phone became less than activity itself and more of a way to communicate while on the go and doing other things. Push-button phones took less time to dial than rotary phones. The beginning of the cell phone era brought a culture that became all about speed and convenience.
Verbal communication is only a small component of today's cell phones. 21st century cell phones have revolutionized and entire new form of communication-- the text message. Smart phones allow users to browse internet, use gps features, listen to their music library, and have a world of "apps" at their fingertips using a touch screen, requiring the most minimal amount of effort. Nanotechnology lets people carry their phones in their pockets. These modern cell phones have created a culture where people are never without their telephone, and everyone is constantly communicating.