Medical examinations often extract localized symptoms rather than systemic observations and snap shots rather than continuous monitoring. Using these methodologies, one cannot discretely analyze how a patient’s lifestyle affects his/her physiological conditions and if additional symptoms occur under various stimuli. We present a minimally invasive implantable pressure sensing system that actively monitors long-term physiological changes in real-time. Specifically, we investigate pressure changes in the upper urinary tract per degree of obstruction. Our system integrates three components: a miniaturized sensor module, a lightweight embedded central processing unit with battery, and a PDA. Our tether-free system measures pressure continuously for forty-eight hours and actively transmits an outgoing signal from an implanted sensor node to a remote PDA twenty feet away. The software in this in-vivo system is remotely reconfigurable and can be updated when needed. Preliminary experimental results of the in-vivo pressure system demonstrate how it can wirelessly transmit pressure readings measuring 0 to 1 PSI with an accuracy of 0.02 PSI. The challenges in biocompatible packaging, transducer drift, power management, and in-vivo signal transmission are discussed. This research brings researchers a step closer to continuous, real-time systemic monitoring that will allow one to analyze the dynamic human physiology.