In particular, in [24], the authors presented a KTC respiration monitoring system based on a piezoresistive sensing element integrated into Velcro support and a low-power electronic conditioning and acquisition section. In addition, the chest band integrates a Bluetooth transceiver to wirelessly transmit the gathered data. Similarly, in [25], [PERSON] et al. presented a wearable device for monitoring respiratory activity, relying on six piezoresistive sensors distributed on the ribcage. They used a piezoresistive textile, realizing a conductive area by knitting silver threads into the fabric. [PERSON] et al. developed a wearable device to monitor breathing based on a piezoresistive smart textile comprising 89% silver nylon and 11% elastane [28]. In addition, the band includes a Wheatstone bridge, a voltage buffer, and an acquisition board. The tests conducted on six volunteers demonstrated that the developed device featured 0.11 V%\({}^{-1}\) sensitivity and a maximum detectable RR of 36 BrPM, although it showed non-negligible hysteresis. [PERSON] et al. introduced a novel wearable device to monitor the RR and HR; it uses two strain sensors placed on the ribcage and abdomen to detect the deformations induced by breathing and heartbeat [29]. Moreover, the integration of a piezoresistive layer can be an immediate solution for functionalizing common fabric. In [30], the authors developed an e-textile by incorporating an embroidered sensor based on a Velostat pressure-sensitive layer and conductive threads. The resulting sensors were used to develop a monitoring unit to detect vital parameters in infants, such as the RR and electrogardiogram (ECG). The sensor's signal was acquired by a microcontroller section and processed to extract the interest parameters using properly tuned digital filters. Moreover, in [26], the authors integrated four ERBs based on conductive silicone tubes into a T-shirt to detect chest and abdomen movements. The ERB's signals were properly conditioned and acquired to monitor the tidal volume with a precision of \(\pm 10\%\). Similarly, [PERSON] et al. proposed VitalCore, a wearable device for measuring respiratory, cardiac, and actigraphy data using electroresistive polymer and inertial sensors [27]. Properly conditioned and acquired sensor signals were used to extract the breathing pattern, cardiac activity, and body movements. In addition, piezoelectric materials are commonly used to develop wearable devices, exploiting their intrinsic capability of generating an electric signal without needing a polarization voltage. In [31], the authors presented an active breathing monitoring sensor based on a piezoelectric transducer-gated thin-film transistor (PTGTFT) for measuring the chest movements related to respiration, enabling high sensitivity and reliability. In [32], the authors developed a chest band integrating a polyvinylidene fluoride (PVDF) sensor for acquiring respiratory movements, the seismocardiogram (SCG), and heart tones. The output signals from the piezoelectric sensor and ECG are gathered simultaneously by a microcontroller-based section which filters them for extracting the information of interest. Specifically, the sensor output signal is amplified and acquired by a microcontroller that samples and filters to extract different information. Another way to record the heart's activity and breathing movements is forcecardiography (FCG), which employs force sensors instead of accelerometers classically used for the seismocardiogram [33; 34]. The two techniques were compared by simultaneously recording the output signals from an FCG sensor and an accelerometer (SCG) mounted on the same electronic board. The signals were amplified, sampled (sampling freq. = 10 kHz, ADC resolution = 14-bit), and filtered to separate the information content at low and high frequencies. The FCG signal shows two distinct components; the first at low frequency (1 Hz range, LF-FCG) and the second at high frequency (10 Hz range, HF-FCG).