The Xbox One Smartglass App is pretty useful. You can navigate your console with it, look at friend activity, respond to messages, and more, but soon, you will be able to view, share, and save in game screenshots from the app. This functionality will be added due to a vote on the Xbox Feedback website, where users can vote on which new features are added to Xbox devices. The screenshots can be found in the Activity feed on profile pages. The update that will allow users to access the screenshot functionality will be released in the coming weeks for both iOS and Android users.