Coaches are constantly seeking more ecologically valid and reliable data to improve professional sporting performance. Using unobtrusive, valid and reliable mobile physiological monitoring devices may assist in achieving this aim. For example, there is limited information regarding professional fast bowlers in cricket and understanding this role during competitive in-match scenarios rather than in simulated bowling events could enhance coaching and physical conditioning practices. The BioharnessTM is a mobile monitoring device and assesses 5 variables (Heart rate [HR], Breathing frequency [BF], Accelerometry [ACC], Skin temperature [ST] and Posture [P]) simultaneously. Therefore, the aims of this research were to assess the effectiveness of the BioharnessTM mobile monitoring device during professional sporting performance using fast bowlers in cricket and this was to be achieved in five research studies. Study 1 presented the physiological profile of professional cricketers reporting fitness data with other comparable professional athletes, with a specific interest in fast bowlers who were to be the focus of this work. The 2nd and 3rd study assessed the reliability and validity of the BioharnessTM through controlled laboratory based assessment. For validity, strong relationships (r = .89 to .99, P < .01) were reported for HR, BF, ACC and P. Limits of Agreement reported HR (-3 ± 32 beat.min-1), BF (-3.5 ± 43.7 br.min-1) and P (0.2 ± 2.6o). ST established moderate relationships (-0.61 ± 1.98 oC; r =.76, P <.01). Reliability between subject data reported low Coefficient of Variation (CV) and strong correlations for ACC and P (CV < 7.6%; r = .99, P <.01). HR and BF (CV ~ 19.4%; r ~.70, P <.01) and ST (CV 3.7%; r = .61, P < .01), present more variable data. Intra and inter device data presented strong relationships (r > .89, P < .01, CV < 10.1%) for HR, ACC, P and ST. BF produced weaker data (r < .72, CV < 17.4%). Study 4 assessed reliability and validity of the BioharnessTM in a field based environment using an intermittent protocol. Precision of measurement reported good relationships (r = .61 to .67, P < .01) and large Limits of Agreement for HR (> 79.2 beat.min-1) and BF (> 54.7 br.min-1). ACC presented excellent precision (r = .94, P < .01). Results for HR (r = ~ .91, P < .01: CV <7.6%) and ACC (r > .97, P < .01; CV < 14.7%) suggested these variables are reliable in the field environment. BF presented more variable data (r = .46 - .61, P < .01; CV < 23.7%). In all studies, as velocity of movement increased (> 10 km.h-1) variables became more erroneous. HR and ACC were deemed as valid and reliable to be assessed during in-match sporting performance in study 5. This final study sought to utilise and assess the BioharnessTM device within professional cricket, assessing physiological responses of fast-medium bowlers within a competitive sporting environment, collected over three summer seasons. The BioharnessTM presented different physiological profiles for One Day (OD) and Multi Day (MD) cricket with higher mean HR (142 vs 137 beats.min-1, P < .05) and ACC (Peak acceleration (PkA) 227.6 vs 214.9 ct.episode-1, P < .01) values in the shorter match format. Differences in data for the varying match states of bowling (HR, 142 vs 137 beats.min-1, PkA 234.1 vs 226.6 ct.episode-1), between over (HR, 129 vs 120beats.min-1, PkA 136.4 vs 126.5 ct.episode-1) and fielding (115 vs 106 beats.min-1, PkA 1349.9 vs 356.1 ct.episode-1) were reported across OD and MD cricket. Therefore, this information suggests to the coach that the training regimes for fast bowlers should be specific for the different demands specific to the format of the game employed. Relationships between in-match BioharnessTM data and bowling performance were not clearly established due to the complexities of uncontrollable variables within competitive cricket. In conclusion, the BioharnessTM has demonstrated acceptable validity and reliability in the laboratory and the field setting for all variables (Heart rate, Breathing frequency, Accelerometry, Skin temperature and Posture) but with limitations for heart rate and breathing frequency at the more extreme levels of performance. Furthermore, taking these limitations into account it has successfully been utilised to assess performance and provide further insight into the physiological demands in the professional sport setting. Therefore, this work suggests that coaches and exercise scientists working together should seek to utilise new mobile monitoring technology to access unique insights in to sporting performance which may be unobtainable in the laboratory or a simulated field based event.