Importing vCards from a website into iOS’s Contacts.app
I expect you found my solution on Stack Overflow but if not you can see the source code and full description at http://www.mobicontact.info or on Stack Overflow

BTW - it involves wrapping the VCARD (.vcf) file inside a Calendar appointment (.ics) which IS handled by mobile Safari.  All the required user agent sniffing and PHP to auto create the calendar appointement is included.  Feel free to use the code, post a comment or up vote on Stack Overflow to spread the word.  Enjoy and good luck.