How do I export my Google Fit data to iPhone and keep it in sync in the future?

I have used Google Fit on my Android phone for a while, and recently switched to the iPhone. How do I import my step counts and other fitness data into Apple Health on the iPhone from Google Fit? Are there cross-platform cloud services that store this data in the cloud and have both iOS and Android clients so that I don't have this problem again the next time I switch phones? I posted the same question on apple.stackexchange.com to get answers from iOS users.