I'm not sure what you're asking - are you wanting to send notifications as chats?

That's an interesting idea. How would you like to view the messages?

It would propably have to be a chat with only one person as a member. But who would then be viewed as the sender?

If it were a chat with two people (the one who performed and action to your content and yourself) it would be weird since then you both would see the message meant only for the other.

Same things i am trying these days. 

Yes it is true Chat plugin do not includes instant icon notification and email notitfacation.

solution for you.

you can wait  september till Slyhne plugin messages will be ready 

http://community.elgg.org/plugins/385010/1.3

or can wait for Juho for next release, hopefully with instant notifications,

I don't think there is any nice way to do this. There is no solution for the questions I asked earlier.

Besides the notifications system will be completely rewritten for Elgg 1.9 so I don't think it is wise to force the chat as one of the notification methods now. Hopefully the new notification system will have it's very own method for site notifications so it doesn't have to rely on messages plugin.

At least my opinion is that notifications (e.g. "User A likes your content B.") and private messages should be two completely separate functionalities.

You can have a look on the SVN version of 1.9 or milestones for Elgg 1.9. That will help you to plan accordingly for your plugin .

I agree with you Juho it is wise to wait 1.9 to see the new notification system