Just download the iHealth MyVitals app on your new smartphone and sign in to your iHealth account.
Your iHealth Lite scale will reconnect automatically and all your old data will be there.
*credit to Sylvain of iHealth Labs EU
https://helpcenter.ihealthlabs.eu/hc/en-gb/articles/360000007769-iHealth-Lite-HS4S-I-changed-my-smartphone-what-do-I-need-to-do-