Provide presence status indicators where user names appear. The plug-in should add an img tag preceeding user names with URI's formatted according to the service's specifications. The img tag should also be an anchor to launch a chat session with the user. The anchor will need to be formatted using the appropriate browser protocol handler for each IM client, which should be configurable by an administrator.
For administration, there should be an option to define a standard template for IM handles and/or a user defined property. For example, a standard template is ideal for corporate installations where every Trac user uses the same ID for IM (or same ID with an added prefix or suffix). User defined property is ideal for public installations where the user accounts are not centrally managed.