With the latest Zoho Planner update, you can now chat to each of your shared users. On clicking a page you can see the list of shared users with status (either online/offline). Now you can chat with the person who is available for chat.
We have also added RSS feeds for your shared pages. You can find this feature in your planner settings page. Subscribe to the RSS feeds and get notified on the changes done by the shared users in your page.
Do give a try and send your feedbacks to feedback at zohoplanner dot com.