An important feature in the mobile area are maps capabilities. There isn't any app in the market that won't improve their value without a map. Apple and Google doing a great job with there Map-SDKs, but sometimes you hit a spot where they won't suit your needs. Maybe for legal reasons or because you hit a bug inside of them. The later was my case, which is happily resoleved with iOS 10. But I needed an alternative that works offline too.