AFAICT, there’s none that will integrate fully / link with intervals.icu
Garmin Index Scale will link thru Garmin Connect and (some) wellness data is forwarded to intervals.icu
There’s also some scales that link to Apple Health, but again Apple Health doesn’t support ALL the data that most scales has. So feeding intervals.icu will also be spotty
You can try fitnessSyncer.com or I think there are other websites which will sync/link it