We have synthesized multifunctional magnetite nanoparticles coated with N-isopropylacrylamide (NIPAM) and a fluorescent modified acrylamide (FMA) monomer. The temperature of the medium surrounding a collection of nanoparticles may be determined by monitoring fluorescence changes in the FMA monomer resulting from the decrease in polarity of the NIPAM copolymer chain with increasing temperature. The possibility to induce localized heating while allowing non-invasive monitoring of temperature, makes these nanoparticles attractive for biomedical applications.