I had/have an algorithm that I use for MLB games. The stats are relatively easy to find and past that it's just trying to figure out what things "matter". I had a lot of fun day dreaming about which things are important to factor in. Some parks are hitters parks, some pitchers walk batters more often, most batters have a better average depending on the handedness of the pitcher, etc. There are thousands of things you can factor in.

If I'm being honest, it didn't make a whole lot of money before I shelved it myself. The most important factor is that the lineups are rarely submitted early enough for me to bet on a full day. Usually I found myself being able to only play the late games, which is typically 4-6 total teams. It really limits the creativity of the lineups.

In the future I'd like to try it with some other sports (NBA is a big one, because the lineup issue shouldn't be as big of a factor, same with hockey). But I don't expect to make millions, it's just a programming problem that's a ton of fun to solve for.