Conditional neuromodulation is a form of closed-loop bladder control where neurostimulation is applied in reaction to bladder pressure changes. Current methods based on external catheters have limited utility for chronic ambulatory therapy. We have developed a wireless pressure monitor to provide real-time, catheter-free detection of bladder contractions. The device is sized for chronic implantation in the bladder muscle. The pressure monitor consists of an ultra-low-power application specific integrated circuit (ASIC), micro-electro-mechanical (MEMS) pressure sensor, RF antennas, and rechargeable battery. Here we describe an overview of the system, including chronic in vivo test data of a non-hermetic polymer sensor package and chronic testing of the wireless sensor in large animal models. Test results show that the packaging method is viable for chronic encapsulation of implanted pressure sensors. Chronic testing of the pressure monitor revealed some obstacles relating to the chosen implant site within the bladder wall. However, chronic wireless device function was confirmed and data quality was sufficient to detect bladder compressions in large animals, with average correlation coefficient of 0.90.