This Addin is looks like from third party not directly from the Google, thats why it giving warning while trying to log in to Google account.

Same problem already reported by Ben Dover, google blocks it because it says its trying to access sensitive information.

I love the idea behind this extension...however it doesn't work at the moment. It asks you to log into your google account and then google blocks it because it says its trying to access sensitive information...oh well, hopefully it will be updated soon so that the problem gets fixed.