Genius for Restaurant integrates with a wide set of third party services. This is the map of what connects, and where the current setup guide lives.
Check the current Genius for Restaurant POS Integration Matrix and the Genius for Restaurants Limitations List. Both change with releases. Confirm against the matrix for the software line the site actually runs, because Genius NextGen and Genius Classic do not always support the same partners at the same time.
Some partners need API keys from the location. See Retrieve API Keys.
Source: Global Payments Genius POS Setup Guide and the Global Payments Genius help center. Newly built article, pending review.