You'd think that Valve's Index headset would have supported Viveport Infinity from the outset given the premium price and backwards compatibility with HTC gear, but not so -- it's only just arriving now. As of August 29th, the Index has access to the unlimited VR service and its library of games, apps and videos. It costs the same $13 per month ($9 if you commit to a year), but there is a perk for splurging on the headset. Anyone with an Index can claim two months of free Infinity access during a promo lasting through all of September, whether or not you're already an Infinity member.