"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
AirPods and AirPower: Everything We Know
Apple Watch Series 2 is Slightly Thicker and Heavier Due to Larger Battery
38mm models of the Apple Watch Series 2 are 11.4mm thick and weigh 28.2 grams, compared to 10.5mm and 25 grams for original 38mm models.
Similarly, the new 42mm models are 11.4mm thick and weigh 34.2 grams, compared to 10.5mm and 30 grams for original 42mm models.
This means that all Apple Watch Series 2 models are 0.9mm thicker and up to 4.2 grams heavier, likely due to the inclusion of an up to 35% larger battery, but the real-life difference on the wrist should be relatively unnoticeable. The width and height of the Series 2 models remain unchanged.
Apple did not confirm that Apple Watch Series 2 models have a larger battery, but it is likely considering that battery life is equal to original models despite the Series 2's inclusion of a faster S2 chip and GPS. A future teardown of the device should confirm the larger battery capacity.