While the features that the article mentions do make sense, I doubt that M7 co-processor is a revolution. I suspect that it's a technical necessity.
First, the quoted article is probably technically incorrect in saying that "Now fitness apps that track physical activity can access that data from the M7 coprocessor without constantly engaging the A7 chip. So they require less battery power."
Fitness apps run on A7, therefore they can't do anything without "engaging the A7 chip". Most likely the accurate story is that M7 is used for collecting data from the sensors when fitness apps are not actually doing anything (and A7 may go to sleep) and from time to time when the apps need the data they get it from M7 (or from the flash memory where M7 saved the data).
The co-processor itself does not add much (if anything) to the type of data that may be collected. It's all about the sensors. I do not know if those are usually placed on the main APU (SOC) or not. If they were moved to M7 there might be some power savings there.
However, the reason why Apple may need a co-processor could be because of the chosen A7 architecture. With two big cores, it's difficult to save power when you need to perform simple computational tasks required for registering sensor data. On the other hand, Samsung may utilize the features of their big/little core architecture where they would simply run one little core on the main APU to do what M7 does. because they can do that.
Weak argument. M7 can be repurposed in other Apple devices that have less processing power. That's why Apple decided it was worth it to spit off those functions and that will work as an advantage to Apple in the long run.