Embodiments of a lumenally-active system and method of use and control thereof are disclosed. According to various embodiments, a lumenally-active device is positioned in a body lumen of an organism, where the device may sense a parameter of a fluid in the body lumen and perform an action on the fluid. Control logic and/or circuitry may be located on the device, or the system may include a separate control module. Liquid or gaseous fluids may be treated by embodiments of the device. Actions may include, for example, modification of a body fluid by addition or removal of a material, or by modification of a property of a body fluid or a component thereof.