Background: There has been an increasing amount of focus on measuring the ICF concept of participation in the rehabilitation of people with aphasia. The amount of time that people with aphasia talk has the potential to be used as an indicator of participation for this population. However, in order to measure talk time, an accurate, portable, and usable biofeedback tool is required. This paper details the development and accuracy testing of the CommFit™ iPhone application, which, paired with a BlueTooth headset, times the talk of the user. Aims: The aim of development of CommFit™ was to maximise the likelihood that the app would be usable by people with stroke and aphasia. Accordingly, aphasia-friendly text principles and other features of accessibility were integrated into the design, which is described in detail in this paper. The purpose of this study was to investigate the accuracy of CommFit™ in quantifying talk time in everyday environments in a small number of healthy adults. Methods & Procedures: Participants were three healthy individuals, who each wore the CommFit™ app with BlueTooth headset and a continuous voice recorder for a total of 10 h in their everyday lives. Talk time registered by the app was compared to the amount of talk time manually calculated from the continuous voice recording to obtain its relative accuracy. Outcomes & Results: CommFit™ measured talk time within ±4% of the actual talk time in an ideal environment with no background noise, and ±13% in everyday environments when a calibration procedure was used. Conclusions: CommFit™ is an app that was developed to be aphasia-friendly and accessible. The accuracy results suggest that the app with headset is a usable and valid indicator of talking time for people with aphasia. Testing will be carried out with the target population to further confirm the usability of the app and its role as an indicator of participation.