Researchers have been focusing on developing intelligent sensing devices capable of capturing human movements or signals, particularly in sports and healthcare. These signals, encompassing biophysical and biochemical data, are increasingly utilized across various fields for purposes such as sports training, medical diagnostics, preventive healthcare, and rehabilitation. The urgency for real-time health monitoring has been underscored by the coronavirus disease 2019 (COVID-19) pandemic, hastening the demand for portable, flexible sensors enabling remote health signal measurement. Our investigation delves into recent advancements in flexible smart sensor technologies tailored for monitoring crucial signals in healthcare and sports. Within this comprehensive study, we provide an overview of the latest progress in smart sensors and systems engineered to track fitness and health indicators. These encompass a range of signals including electrocardiograms (ECGs), inertial data, motion, heart rate, and biological fluids (such as blood and sweat). Furthermore, we introduce a novel approach involving multimodal and integrated multidimensional sensing systems distinguished by their high sensitivity. Additionally, we elucidate current challenges in the field and offer insights into the future trajectory of smart sensors in capturing vital signals effectively. It is evident that the integration of modern fabrication techniques, stretchable electronic devices, the Internet of Things (IoT), and artificial intelligence (AI) algorithms has significantly augmented the capacity to monitor and utilize these signals for human health monitoring, including disease prediction. Smart sensors and systems that are multidimensional and multimodal might provide a more adaptable and comprehensive solution to meet the escalating healthcare demands.