I don't know the exact method, but I've seen before where a user creates a post and then embeds the upvote button for that post into their website.
You may be able to do that with your app as well, or maybe incorporate a feed of your content and encourage users to upvote there.
That makes sense. Wondering how we could also incorporate it into tip jars and subscriptions? Either way, we want to incorporate some form of this into our app.