Study aim: the aim of this study was to compare the accuracy of a contactless photoplethysmographic mobile application (CPA) to record post-exercise heart rate and estimate maximal aerobic capacity after the Queen’s College Step Test. It was hypothesised that the CPA may present a cost effective heart rate measurement tool for educators and practitioners with limited access to specialised laboratory equipment. Materials and Methods: seventeen participants (eleven males and six females, 28 ± 9 years, 75.5 ± 15.5 kg, 173.6 ± 9.8 cm) had their heart rate measured immediately after the 3-min test simultaneously using the CPA, a wireless heart rate monitor (HRM) and manually via palpation of the radial artery (MAN). Results: both the CPA and MAN measurements had high variance compared to the HRM (CV = 31 and 11% respectively, ES = 1.79 and 0.65 respectively), and there were no significant correlations between the methods. Maximal oxygen consumption was estimated 17% higher in CPA compared to HRM (p < 0.001). Conclusions: in conclusion it is recommended that field practitioners should exercise caution and assess the accuracy of new freely available technologies if they are to be used in practice.