John Brownlee, writing for Fast Company on support for wheelchair users in watchOS 3:

Each test subject was allowed to use their own wheelchair, which they fitted with special wheel sensors. In addition, many were outfitted with server-grade geographical information systems, which collected extremely precise data on their movements through the world. The number of calories burned, meanwhile, were determined by fitting test subjects with oxygen masks, and precisely measuring their caloric expenditure as they pushed.

In the end, Apple collected more than 3,500 hours of data from more than 700 wheelchair users across all walks of life, from regular athletes to the chronically sedentary, in their natural environments: whether track or trail, carpet or asphalt. From this data, they learned how to adjust watchOS 3’s algorithms to track wheelchair users.

This is the kind of work that truly makes an impact on how people live their lives.