The remote sensors use the Laird 654 series Bluetooth module, based on the nRF52840 (Laird PN 451-00001). That Laird module includes a trace antenna and is FCC certified. The actual motion sensing is done with an LIS2DH12. We just had 75 of our PCBs fabricated and assembled at PCBWay in China, and I’m about to open the box and see how they check out.