The download button opens the iTunes App Store, where you
may continue the download process. You must have iTunes installed with an
active iTunes account in order to download and install the software. This
download may not be available in some countries.
From Airwire products.:
Thanks for -App store(United Kingdom) "Healthcare&Fitness category Rank.21"App store(Japan) "Healthcare&Fitness category Rank.16"Weight+ can register Body mass data Point to Health app for Apple Watch.Features - Add Weight and Body Fat Percentage by using your WATCH - Sophisticated UI for Digital CrownApple Watch supported by later than iPhone5 models.Previous models than iPhone4S (Including iPod touch) is not able to use Apple Watch.