You didn't think Twitch would offer streamer extensions without finding a way to generate money from them, did you? Sure enough, the customization feature now accepts Bits (the microtransactions you normally use to tip streamers) for on-page games and other features. Chip in a few cents and you can participate in games with broadcasters (such as arcade or trivia titles), predict who's likely to win and mess with the streamer by voting in polls that decide what they do next.
The support is available today through dozens of extensions on launch, and it's available to both Affiliates and Partners.
No, the thought of having to pay just to interact with a streamer isn't thrilling -- some of these features have been available for free, including channel bots that don't require extensions. This does give you a better reason to buy Bits outside of pure financial support, however. And it's not just another source of revenue for Twitch streamers -- they can use it as a gatekeeper that keeps (some) trolls out of on-stream events. There is the chance that hosts could misuse their newfound power, but it could also create new opportunities.