I am not a security administrator. I am a software developer, so there may be more examples of it than what I can share. One example of such an SSH gateway that I am aware of is: Balabit Shell Control Box. For details, see http://support-public.cfm.quest.com/46282_scb-guide-admin.pd... (see section 7.5. Procedure - Creating and editing channel policies and section 11.2. Supported SSH channel types).