Since end users may skip over the full descriptions, I propose that the manifest allows a developer to specify which SDK the app was built with, or to indicate the minimum version of firmware for each watch that it is compatible with. For example:
<iq:product id="vivoactive" firmware="2.70" />
The connect app on the phone could query the watch for firmware and gps version when it syncs. Then when browsing the store via the connect app it can check the minimum firmware permitted for a given app and indicate to the user that their firmware must be updated to use that particular app, preventing them from installing it until they have.