I used to have an arbitrage subscription for a site called satoshi signals , and same they were able to scan the odds from all bitcoin bookies and post the higher odds
Well I guess you could do it that way, and just scan that site. When I first read your idea I thought that you actually wanted to create one website that would allow users to interact directly with other bookies. Since you said:
In order to do this, you would need to use an API. If you just want to scan bets, and show the best available odds from a list of bookies, then users would not deposit in that website, and would need to go to the listed bookie and make their bet with their platform, as they normally would.
It's still a good idea. Not as convenient as using just one site, but still a great service.