Dont think you can turn off the M7 chip / step tracker. At best you might want to disable "Motion" for specific apps (but not Health, thats not an option) under Settings > Privacy > Motion Activity as well as other Privacy > Location Services apps and such you dont want to use (to save battery).
I submitted the feedback to change units for Health cos even though Im in the right 'Region', there are certain things (like glucose) that I have information for in one measurement - not the one the app uses.
Couldnt find the submit button on the feedback form, so just pressed enter to submit the form đ
Also couldnt find 'Health' as an app, so just submitted it under "iPhone". Also couldnt select ios 8 from the ios version list because its not listed! looks like Apple has a lot of updating to do on their site as well!