@gilesgoat Several Vive 3.0 trackers. I've written plenty about trackers over the past several months, but there are a few systems out there like SlimeVR, Fluxpose (soon), Vive/Vive Ultimate, HiratoraX, Tundra, etc. Most of them have inside-out tracking that register positional data from the devices themselves versus an outside-in style used for Vive and Tundra which require base stations/lighthouses to see and track positional data from the trackers from their fixed positions. Lighthouse based setups are more accurate and less prone to drift but could be more expensive given the need for the lighthouses and suffer from occlusion (and Vives are bulky and have less battery life than many others). Outside-in setups are typically lighter and smaller, and are occlusion-free but do require more devices to reach a similar level of quality as lighthouse based ones, suffer from drift, have more wireless interference issues. Really, if you don't need base stations, it's a big investment I probably wouldn't recommend.