Systemic low-frequency oscillations (sLFOs) are non-neuronal oscillations at 0.01–0.15 Hz. These sLFOs travel through the entire body and the brain with symmetrical (across the midline of the body) and highly predictable delays, where they can be observed with functional near-infrared spectroscopy (fNIRS) and blood oxygen level-dependent functional magnetic resonance imaging. Their characteristics may serve as useful biomarkers for detecting and monitoring circulatory dysfunction. Pure sLFOs can be collected in the periphery (e.g., fingers, toes, earlobes). Here we present a 7-channel NIRS oximeter [MNO] for sLFOs detection and analysis in the periphery, which we named concurrent continuous wave fNIRS system (CON-CW fNIRS). Our CON-CW fNIRS is small (10 × 10 × 20 cm³), highly portable, has low-power consumption and is highly cost-effective (below $300). We show that our device is highly reliable and can reproduce values acquired with a commercial fNIRS device with direct comparison (r_max = 0.908 ∆[HbO] and r_max = 0.841 ∆[Hb]) and when compared to previously published data.