A moisture-sensitive device is provided that includes a fluid-sensitive battery. Exposure of the battery to urine or some other fluid causes the battery to provide a voltage that can be used to power a transmitter. The transmitter can then provide a wireless transmission indicative of the battery having been exposed to the fluid. This moisture-sensitive device can be provided in a diaper and transmissions produced by the device can be detected using a smart phone or other device and used to indicate to a user that the diaper has been soiled. By powering the transmitter using the fluid-sensitive battery and storing the battery in a dry state, such a device can be stored for a protracted period of time before use.