This paper describes the current state of our ongoing work developing tools for tracking player enjoyment in traditional face-to-face tabletop gaming situations. The challenge presented is that of quantifying game enjoyment whilst minimising the effects of the measurement techniques on the validity of the study. This paper presents the development of a self-report tool for cellular phones that aims to gauge player enjoyment with minimal impact on the "magic circle" of play. Its design for non-invasive and meaningful selfreport data is described along with initial preliminary results from casual trials that indicate the potential value of the technique along with avenues for further study. Keywords Ecological Validity, Magic Circle, Flow, Fun, Entertainment, Board Games ACM Classification Keywords K.8.0 [Computing Milieux]: Personal Computing ? Games, J.4 [Social and Behavioural Sciences]: Psychology