The fitgem_oauth2 gem allows developers to use the Fitbit API. Certain parts of the code, structure, and the API are heavily based on the fitgem gem which uses OAuth 1.0 for accessing the Fitbit API.
Add the following line to use the fitgem_oauth2 gem
gem 'fitgem_oauth2'
If you are using fitgem_oauth2 in a Rails application, we have a sample rails application to test out the gem. It is available here https://github.com/gupta-ankit/FitgemOAuth2Rails