Embodiments of the invention provide devices and systems to monitor fullness of a patient's bladder. One embodiment of a bladder fullness (BF) measure system comprises a sensor device (SD) and a controller. The SD generates an output signal (OS) based on the force exerted by the bladder against SD the wherein the OS corresponds to a degree of BF. The SD may be attached to the bladder wall or adjoining tissue and positioned between the bladder and the pubic bone such that the SD is not affected by tissues force other than that from the bladder. The controller connects to the SD and causes an associated implant to perform a function when the SD output signal exceeds a predetermined threshold. Embodiments are particularly useful for providing information on BF to patients suffering from spinal injury or other conditions whereby they have lost the ability to sense BF and/or voluntarily urinate.
