In this talk I will present an overview of the upgrade to the polarization-sensitive camera on the Atacama Cosmology Telescope known as Advanced ACTPol (AdvACT). This upgrade targets ambitious science goals using advanced technologies including dense arrays of cryogenic bolometers with superconducting sensors and continuously-rotating silicon-metamaterial half-wave plates for modulation of incoming polarization. I will discuss work on the detector arrays, advances in our understanding of our bolometers, and the data processing pipeline under development to handle polarization-modulated data.