I just installed the iOS Pacer app to see if I can restart checking my daily step count. Whilst for me there's a lot of bloat it looks ok.
The interesting bit: I can see the last week of steps which implies the iPhone 6 records stuff with no app necessary.
Yes, or course I've a question: what's popular, what's 'better'?
Pacer - Pedometer plus Weight Loss and BMI Tracker by Pacer Health, Inc
https://appsto.re/gb/CDHYJ.i