From time to time, Cisco builds ntop-friendly products. This is the time of the Cisco ON100 network agent.
This tiny device that can fit on your hand, has been integrated with ntop for the purpose of traffic monitoring as you can read on this technical note Enabling ntop Packet Monitoring with Cisco OnPlus Service.
ntop is an optional application watching the second LAN port (Monitor port). The Cisco cloud service provides a web tunnel back to the ON100 to ntop’s web service. No data is interpreted, as ntop does that. This way end users can use ntop application without needing to invest in a PC. The ON100 unit has lots of CPU/RAM and ntop seems to behave very well. Since customers can use either (or both) port mirroring or NetFlow, everyone is happy.
You can find more about ntop and ON100 at this discussion page.