These integrations are all made by our partner companies. For customers that use both systems, they make these integrations to act as connections between the two. There are no extra charges from Clio for using the integrations, however, there may be restrictions from the other company as to which plans have integrations available to them.
You will need an account (most likely paid) with the integration company, even as a Clio customer. Their prices should be available on their websites.