Envolve Chat - A customizable chat toolbar for your website
Envolve provides Single Sign On, so that users who already have accounts on your site are automatically logged into chat. Users who are not logged into your site can login with Facebook, Twitter, or chat anonymously if you would like to allow that. You also have the option of restricting chat to only be displayed to users who are logged into your site.
A free, ad-supported version is available for up to 25 simultaneous chatters. Paid versions are available for larger sites and for sites that want to remove Envolve's branding from the product. Pricing information is available here.
Yes. This is a new feature as of version 2.1 of the plugin.