The Essential Phone is built to be a pro consumer device, and the magnetic accessory port is meant to fill in the gaps that 24 - month upgrade cycles can't. (9to5google.com)
The Essential phone offers a lot of promise thanks to its expandable accessory port, stock Android interface and nearly bezel-less screen design. (techradar.com)
There is also a smart accessory port on the Pebble Watch that can be used by developers to create sensors and smart straps. (iphonehacks.com)