I have developed a proof-of-concept that exports all of my Centric CRM contacts and accounts to vCards for use with cell phones, email applications and even the Blackberry. The project is for internal use but I can't say whether my company will be interested in selling or open sourcing this component. I'll update this thread when I know!
The Java application uses the fantastic XML-HTTP API to download the contacts database and my company's own vCard library to create vCards. It currently exports vCards from Centric but cannot import vCards into Centric.
One major bug that hurts this tool is issue 681: "Missing methods in the XML API"
https://www.centriccrm.com/ProjectManagementTickets.do?command=Details&pid=48&id=1300
Cheers,
Jesse