This paper presents the Instant Customized Summaries Streaming service, a multimedia service able to deliver customized video summaries with a minimum delay after the original content has been uploaded to a video repository. Uploaded videos start being analyzed, via on-line real-time algorithms. As analysis results are available, video summaries are then generated also in an on-line scheme, adapted to different available terminal and finally streamed to the subscribed clients. The whole chain works in on-line mode so all the processes can be simultaneously executed without waiting for any of them to have finished its operation. A prototype of this service, accessible via a web interface, has been fully implemented.