There aren’t' too many devices that you can look at and instantly 'get' that they led to near-instantaneous changes in the way the world functions and behaves. Radios and TVs certainly did, as did the affordable automobile. We can toss in the microwave oven, the X-ray camera, and the personal computer as well. Most recently, the honor would have to go to the cell phone and, in particular, the iPhone.
Apple's baby is widely regarded as the most ubiquitous, and most forward-thinking, of the now borderline-essential cellular handsets. For better or worse, it's transformed the way we do business, play games, take pictures, and interact with our friends and families.