Ovi Contacts could be integrated with the phonebook or contact list by creating a 'field' for ovi contacts usernames. When I add or edit a contact in the phonebook, I will be able to add his/her ovi/gtalk username or choose from an existing username that I've already added in Ovi Contacts. Then from there you can have an option to"chat" with the contact through Ovi Contacts. Even better, the Ovi Contacts display picture could also be synchronised with the contact image in the phonebook. Another great thing would be if the status information (Available, Away, etc.) could be seen with an indicator next to the person's name in the phonebook itself. There is an empty space to the left of the contacts' names so that could be used to show the online status of the contact.
This isn't very essential right now and especially at this stage of development, but it will be great to see this sort of integration in future versions.