In this paper, we summarized power and latency challenges of eye tracking systems for mobile XR glasses. Compared to conventional ET applications like psychology or neuroscience experiments, or user interface for people with disability, XR glasses require a lot lower power consumption considering overall XR system power budget, which is less than ~1W with battery power. At the same time, latency is also important since if ET latency is too large so that it is difficult to accommodate the ET and graphics rendering within the target XR’s motion-to-photon latency, then users feel motion sickness. Considering the challenging ET’s power and the latency requirements in XR, we will introduce several factors that could impact on power and latency in both algorithm and system-level in this paper. Also, we will share rough power and latency exploration results to see how challenge it is to meet such two requirements at a same time. In addition, we reviewed commercial eye tracker’s power and speed performances to see if they can provide enough performance for the XR applications. Lastly, we will introduce some promising academy researches using ET embedded image sensor to satisfy both power and latency challenges in XR.