Each week Ross Rubin contributes Switched On, a column about consumer technology. In the golden era of the PDA, many debated whether future consumers would adopt a one-device or two-device approach. The two-devicers argued that the connectivity for phone calls would come from a simple, bare-bones cellphone while all the fancy data management would occur on a Bluetooth-tethered, PDA-like device unbound from cellular contracts. The Handspring Treo was for many the first converged-device handset that accomplished key tasks well enough to make a convincing case for handset integration, and the smartphone revolution ensued. The first iPhone featured a large screen for
