The Project 8 collaboration is commissioning a third-generation neutrino mass experiment, the Cavity CRES Apparatus (CCA). The CCA will use a resonant microwave cavity to detect the cyclotron radiation given off by trapped electrons, aiming to demonstrate Cyclotron Radiation Emission Spectroscopy (CRES) with sub-eV resolution near the 18.6keV tritium β-decay endpoint. CRES converts the initial energy of trapped electrons into a microwave-frequency signal via cyclotron motion in a trapping magnetic field, so an absolute energy calibration requires knowledge of the absolute magnetic field. At the tritium endpoint, an absolute energy calibration with an accuracy of a hundred meV requires a magnetic field calibration better than 0.2 parts per million. Helium-3 magnetometry is an excellent candidate technique for mapping the Project 8 magnetic field, capable of accuracy and precision at the parts per billion level. In this talk, we describe progress towards a high-sensitivity helium-3 NMR magnetometer operating near 1 Tesla that can characterize the trapping field in Project 8 with the required accuracy and precision.