We present a service providing real-time feedback to participants of small group meetings on the social dynamics of the meeting. The service measures and visualizes properties of participants' behaviour that are relevant to the social dynamics of the meeting: speaking time and gaze behaviour. The dynamic visualization is offered to meeting participants during the meeting through a peripheral display. Whereas an initial version was evaluated using wizards to obtain the required information about gazing behaviour and speaking activity instead of perceptual systems, in the current paper we employ a system including automated perceptual components. We describe the system properties and the perceptual components. The service was evaluated in a within-subjects experiment, where groups of participants discussed topics of general interest, with a total of 82 participants. It was found that the presence of the feedback about speaking time influenced the behaviour of the participants in such a way that it made over-participators to behave less dominant and under-participators to become more active. Feedback on eye gaze behaviour did not affect participants' gazing behaviour (both for listeners and for speakers) during the meeting.