There are probably unified services that let you do it - I was kinda competing in this area but didn't want to deal with enterprise sales, and it's a bit of a h

There are probably unified services that let you do it - I was kinda competing in this area but didn't want to deal with enterprise sales, and it's a bit of a hard sell anyway. If you do it individually, there are public developer docs for each exchange that explain how their API works. It's generally free as long as you're not making a large number of active trades.