Lumen-traveling devices and associated methods and systems are described. Lumen-traveling devices capable of traveling within a body lumen may include a propelling mechanism to produce movement of the lumen-traveling device within the lumen, as well as additional components such as a sensor, an active portion, and/or control circuitry. In some embodiments, a sensor may be used to detect a local condition, and an action may be performed within the body lumen. Actions that may be performed include, but are not limited to, transmitting information, releasing a material within the lumen, performing a surgical step, or collecting a sample, among others.