A device useful for oral drug delivery device consisting of: (a) a capsule, tablet or pill designed to disperse in the gastrointestinal system; (b) an RFID tag positioned in the capsule, tablet or pill, the RFID tag comprising an antenna; (c) an object selected from the group consisting of a magnet, a ferromagnetic object, a ferrite object and an electromagnetic shielding object positioned within, over or adjacent the antenna of the RFID tag to alter the antenna characteristics of the RFID tag so that if the RFID tag is interrogated before the capsule, tablet or pill disperses in the gastrointestinal system, the response of the RFID tag is sufficiently altered or attenuated to determine that the capsule, tablet or pill has not dispersed in the gastrointestinal system and so that if the RFID tag is interrogated after the capsule, tablet or pill has dispersed in the gastrointestinal system, the object separates from the RFID tag so that the response of the RFID tag is sufficiently detectable to determine that the capsule, tablet or pill has dispersed in the gastrointestinal system. Alternatively, a switch can be used to signal ingestion of the device, and change the response of the device.