We present a new miniaturized (below 1mm3) temperature sensor based on micro-fluidic technology and radar passive interrogation principles, that can be easily applied for temperature telemetry for medical applications. The chipless micro-system is made up of a planar-gap capacitor with a micro-channel located in between its plates. The temperature-dependent expansion/shrinkage of the water inside the micro-channel modifies in a monotonic way the liquid level across the capacitor. The resulting change in the effective permittivity modifies the capacitance value in a temperature-dependent way. The first prototypes of the temperature micro-sensor were micro-machined and integrated with an antenna, while the ambient temperature was remotely measured using FMCW radar interrogation principles at 29.75 GHz. Preliminary measurement results demonstrated a 0.4dBm/°C sensitivity over a 9°C temperature range (24°C-33°C).