Extensive research shows that there is a close correlation between a disease diagnostic and the patient’s exhale breath gas composition. It has been demonstrated, for example, that patients with a diabetes diagnosis have a certain level of acetone fume in their exhale breath. Actually, symptoms from many other diseases could be easily diagnosed if appropriate and reliable gas sensing technologies are available. The COVID-19 pandemic has created demand for a cheap and quick screening tool for the disease, where breath biomarker screening could be a very promising approach. It has been shown that COVID-19 patients potentially present a simultaneous increase in ethanal (acetaldehyde) and acetone in their exhale breath. In this paper, we explore two different sensing approaches to detect ethanal/acetone, namely by colorimetric markers, which could for example be integrated into facemasks, and by a breathalyzer containing a functionalized quartz crystal microbalance. Both approaches can successfully detect the presence of a biomarker gas on a person’s breath and this could potentially revolutionize the future of healthcare in terms of non-invasive and early-stage detection of various diseases.