Many web site use 3322.org's dynamic DNS service. Orignally, 3322.org provided two clients for both windows and *NIX. For OSX and other OS, you can use this client. If you like, you can embeded it in your own application.
Initiated by the EPIC Consortium, this project aims at developing a RESTful webservice for managing PIDs with the Handle System developed at CNRI.
Additionally, some RESTful clients in various commonly used languages will be developed.