Cavitas sensors that are attached to body cavities, such as the contact lens and mouthguard, have been developed and demonstrated. Being neither implanted nor worn, the cavitas sensors have many advantages for the noninvasive biosensing of chemicals in the permanent body fluid in human body cavities. A soft contact lens (SCL) biosensor for monitoring the sugar content in tears was fabricated using biocompatible polymer and bio-MEMS techniques. It performs real-time monitoring of tear sugar content, which reflects the level of blood glucose. In addition, a wireless mouthguard glucose sensor system for diabetes mellitus has also been developed by incorporating a small potentiostat and a Bluetooth 4.0 low-energy (LE) transmitter to a transparent mouthguard. In the near future, such self-detachable cavitas sensors will allow us to obtain biochemical information, thus improving the quality of life and living standards through daily medicine (health care and presymptomatic and preventive medicine).