Right now, only one of the interactive options appears to be free -- the "Modern Sport - Rhine" by watchmaker MVMT. If you set that as your watch face, tapping the company's logo opens a website on your phone. You can't customize this at all, so it's not like you can change it to launch something more useful. This free option is basically an ad.
The other available interactive faces are more intriguing, and range in price from 99 cents to $1.99. There's "TD | Your Multi G077 D," which lets you scroll through your metrics like steps, calories and heart rate and "MbM - Triple Fruity." On the latter, you can tap the bottom dial to switch the watch's background (choose between a watermelon, a kiwi or a lemon), or hit the top dial to launch the Weather app.
There's also "World Cup Oracle," which is a mini game that lets you match up soccer teams and see who wins, according to a compass-like wheel of chance. A couple other options let you play simple games like flicking away a digital spider or touching your screen to watch water ripple.
Other than quickly swapping designs or scrolling through on-face stats, few of these interactive watch faces are very useful right now. At least, they're not useful enough that I'd want to pay $2 to use them yet. As more of Facer's community of developers create interactive faces, though, future offerings may actually be compelling. In the meantime, if you're looking for a new look for your smartwatch, Facer's library offers a ton of regular non-interactive designs, many of which are free and pretty.