The multifunctional nanodevice described here integrates nanoscaled imaging, targeting, and controlled drug delivery, as well as the capability to monitor, in situ, the amount of drug released from the nanodevice with single-cell resolution. The nanodevice is composed of a polymer core/single-crystal iron oxide shell nanostructure bonded to a quantum dot. It shows outstanding release and retention characteristics via an external on/off manipulation of a high-frequency magnetic field. Upon magnetic stimulation, the single-crystal iron oxide shell demonstrates formation of nanometer-sized polycrystal domains of varying orientation. This allows a variation between retention and slow release of the drug. Further stimulation causes permanent rupturing of the shell, causing release of the drug in a burst-like manner. The quantum dot bonded to the nanodevice provides optical information for in situ monitoring of the drug release through use of a magnetic field. Remote control drug release from the nanodevice in a cancerous cell line (HeLa) was successfully accomplished using the same induction scenario. When nanodevices equipped with quantum dots are taken into cancerous cells, they are able to provide real-time drug dose information through a corresponding variation in emission spectrum. The nanodevice designed in this study has achieved its potential as a cell-based drug-delivery system for therapeutic applications.