Accurate assessment of gastric motility is essential for improving the safety and efficacy of enteral nutrition therapy in elderly patients and individuals with dysphagia undergoing percutaneous endoscopic gastrostomy (PEG). However, a reliable method for long-term, low-invasive, and stable monitoring of gastric motility is yet to be established. We developed a novel measurement system designed to monitor gastric motility by detecting intragastric pressure fluctuations through a pressure sensor affixed to a gastrostomy tube. This system conceptualizes the stomach as a single balloon, enabling real-time, low-invasive recording of pressure variations associated with gastric contractions. For preliminary evaluation, we evaluated the capability of the system to capture responses comparable to electrogastrography (EGG). We performed simultaneous 30-min recordings of EGG and intragastric pressure signals before and after nutrient infusion in a cohort of 20 PEG patients. Furthermore, we analyzed frequency- and time-frequency-domain features using fast Fourier transform, wavelet transform, and coherence analysis. Before infusion, the average dominant frequencies (DFs) of both signals were comparable, indicating no systematic bias between methods. The average coherence was 0.32 ± 0.10, suggesting a low-to-moderate correlation. Following infusion, the DF remained consistent across both methods, with a coherence of 0.30 ± 0.06. These findings suggest that the intragastric pressure signals reflect gastric motility to a degree similar to that of EGG. In conclusion, the proposed system shows the potential as a practical and effective tool for visualizing gastric motility in PEG patients.