Let the members of your site post an update to their activity stream from anywhere in your site or any other subsite in a multisite installation inste
This is a simple that adds an activity button to the admin toolbar in the fron-end. Once a user (logged in) clicks on the button the activity form will pop up. The form will have a text area for the user to enter anything he want to post in his activity. When the user submit the form the plugin will post the info to his activity stream.
Checkout the premium version for extra features