marco_b

This is a plugin / widget, after installing you have the possibility to locate a widget to your site. An visitor can now send a sms to a person.

SMSPlug

With this plugin you can use the service from aspsms.com. It allows you to send sms via their service.

richardphelps

This plugin allows users to chat in real time using AJAX. Users can connect with any other users.
Use the [bp-instant-chat] shortcode to embed the front end chat on any page.

BuddyPress Instant Chat

Instant chat plugin for BuddyPress allowing user to connect and talk in real time.

SMSPlug vs BuddyPress Instant Chat