I've just read on the Nokia Betalabs blog that the formerly known Nokia Chat application has been renamed to Contacts on Ovi. What really surprised me is to know that there is a version available for the Internet Tablets since last October. I have not been able to test it yet, but it seems that it is simply a plugin for the Accounts program which enables the user to register his Ovi account and start chatting.
In the FAQ page it is also noticeable that you can register your Ovi account as a standard Jabber/XMPP account in other instant messaging clients such as Pidgin and Adium.
To download the package, just point the browser of your tablet to this address or download it directly form here.