Lumen-traveling devices capable of controlled material release 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, a material release portion, and/or control circuitry. In some embodiments, a sensor may be used to detect a local condition, and a material may be released from the device in response.