The Google+ API allows you to create interactive posts you can share from your website, which contain a call-to-action button with an image and details from the link you want to share. The API lets you pre-fill the text the user can use to share your link (something which Facebook as removed from their API), and gives you options to add in deep-links for mobile apps too.
You can customise the following attributes:
data-contenturl– the URL you want to share
data-contentdeeplinkid– the deep-link URL
data-clientid– Client ID from Google APIs Console
data-prefilltext– The text you want to pre-fill for the user
data-calltoactionlabel– label for your call-to-action button, see the full list here.
data-calltoactionurl– URL for the call-to-action button. The content URL and the call-to-action URL must match for the post to work.
data-calltoactiondeeplinkid– the deep-link URL for the call-to-action
It is currently not possible to track sharing of the interactive post, but it is possible using the standard Share button.