It’s easy to see the appeal of Project Ara, Google’s modular smartphone concept. With Ara, a dead battery in the middle of a day trip doesn’t set off a frantic search for someone with a charger. Instead, you pop in a spare. A cracked screen wouldn’t mean buying a new phone, or turning to Craigslist to find a shady, warranty-voiding replacement. It would just mean swinging by the mall to pick up a new one.