If you've searched around this space at all, you've probably run into the term "matched betting." It's not a new invention — it's been a known strategy for years, mostly built around exactly the mechanic this tool automates. Worth knowing what the term actually means before assuming it's more complicated than it is.
The idea has one moving part: place two opposing bets on the same event, at two different sportsbooks, sized so that your total outcome is close to identical no matter which bet wins. Normally, betting both sides of the same game is a losing move — the odds are built so the book keeps an edge either way. What changes the math is the bonus bet on one side. Because that leg is "free" money to begin with, the combined position can come out ahead even after accounting for what you lose on the side that doesn't hit.