Warframe will be one of the first games to use the feature.
You won't need Razer gear, of course. "Most" USB and wireless peripherals will work with the Xbox One. Also, this doesn't mean you can expect it in every game, or that developers will produce titles expecting users to try it. Compatibility will come on a "title-by-title basis," and support won't be switched on by default. Microsoft knows there's a risk of creating games that virtually require a mouse and keyboard for competitive multiplayer modes (first-person shooters in particular), and it's promoting the creation of games that are "fun, fair and correctly balanced."
Still, it's uncertain just how this will shake out. There have been ways to use mice and keyboards in console games before, but they've typically been unofficial solutions that haven't received widespread adoption. Native in-game support changes things -- it will now be relatively easy to plug in and potentially claim an unfair advantage. It may take some time before it's clear just how well developers walk the fine line between a handy feature and giving some players a way to 'cheat' against their gamepad-only counterparts.