INTRODUCTION: Perineal descent is a phenomenon associated with anorectal dysfunction. It is diagnosed by defecography but subjected to manual measurements on the images/videos and interobserver bias. Fecobionics is a simulated feces for assessing important physiological parameters during defecation. Here, we translate Fecobionics into a new method for estimation of perineal descent based on electronic signals from the embedded inertial measurement units (IMUs). METHODS: A displacement measurement method by a combined zero-velocity update and gravity compensation algorithm from IMUs was developed. The method was verified in a robot model, which mimicked perineal descent motion. RESULTS: The method correlated well with the reference (R2 = 0.9789) and had a deviation from the peak displacement (range 0.25–2.5 cm) of −0.04 ± 0.498 cm. The method was further validated in 5 human experiments with comparison to the benchmark defecography technology (R2 = 0.79). DISCUSSION: The proposed technology is objective, i.e., electronic measurements rather than by fluoroscopy or MRI. The development may impact clinical practice by providing a resource-saving and objective technology for diagnosing perineal descent in the many patients suffering from anorectal disorders. The technology may also be used in colon experiments with Fecobionics and for other gastrointestinal devices containing IMUs such as ingestible capsules like the Smartpill.