This paper discusses the aspects of data reliability and user privacy for the emerging practice of mobile phone based contact tracing for the COVID-19 pandemic. Various countries and large technology companies have already used or plan to design and use mobile phone based solutions, in an effort to urgently expedite the process of identifying people who may have been exposed to the disease and limit its spread to the general population. However, serious concerns have been raised both in terms of the validity of the collected data as well as the extent to which implemented approaches can breach the privacy of the mobile phone users. This review examines the weaknesses of existing implementations and concludes with specific recommendations that can contribute towards increasing the safety of infrastructures that collect and process this kind of information, as well as the adoption and acceptance of these solutions from the public.