"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
Kanex's 'GoPower Watch' Portable Battery for Apple Watch Now Available for $100
GoPower Watch has a built-in magnetic charging puck, the same one that comes with the Apple Watch, and a USB port for simultaneously charging an iPhone with a Lightning cable. It has pass-through charging while connected to power via Micro-USB, meaning that Apple devices charge first, and then the battery pack recharges.
To charge an Apple Watch or iPhone, simply press the button on the front of the GoPower Watch. The LED indicator displays battery levels and charge status.
GoPower Watch is available in Space Gray for $99.95 on Kanex's website. The portable battery works with all 38mm and 42mm Apple Watch models.