This paper presents a 36nW high-accuracy subthreshold oscillator-based temperature sensor in 180nm. The proposed super cut-off contention-free (SCCF) delay cell closely mimics the temperature dependency of a single MOS, leading to bestin-class -$0.072/+0.082^{\circ}\mathrm{C}(\pm 0.27^{\circ}\mathrm{C})$ inaccuracy after 2-(1-) pt calibration. A compact voltage regulator with three native transistors realizes 0.02%/°C line sensitivity and 1mK noise floor. A uniform resolution frequency to digital converter (FDC) keeps the sensing resolution constant across a wide temperature range. In addition to standard testing, the 1-pt calibrated sensor was demonstrated for in-vivo animal body temperature tracking and outperformed off-the-shelf solutions.