Just download the iHealth MyVitals app on your new smartphone and sign in to your iHealth account.
Your iHealth HS5 scale will be recognized automatically.
*credit to Sylvain of iHealth Labs EU
https://helpcenter.ihealthlabs.eu/hc/en-gb/articles/115005873949-iHealth-HS5-I-have-a-new-smartphone-what-should-I-do-