Smart watch for cash walk app

I bought a Samsung galaxy watch4 for the purpose of using the cashwalk app on it so I wouldn't have to carry my phone on me all the time to get coins... But Google play says that it is not a compatible device. 

So I want to get a new watch that would be compatible. I was looking for the cheapest option but does anyone know which devices are compatible?? 

I'm thinking I might get a Fitbit next, but I'm open to all ideas.