The update adds over 100 new activities that you can choose for your workouts. The original version only included running, walking, and biking; but, the new version adds tons of options, including: Australian football, badminton, basketball, calisthenics, curling, dancing, elliptical, fencing, gardening, hiking, ice skating, jumping rope, kickboxing, MMA, P90X, Pilates, polo, rowing, sand running, soccer, spinning, surfing, volleyball, yoga, and Zumba. It is a really, really expansive list, and may be the most inclusive activity list we've seen in any fitness app.
Google Fit is also trying to help make your smartwatch a bit more independent. There is improved Android Wear support, as well as a new experimental feature to keep tracking your steps when your watch is disconnected from your phone. This would mean you could still get a step count if you go out for a walk/run with your Android Wear device but without your phone, or if your phone happens to die before your watch does (which seems the less likely scenario).
Download: Google Fit