Android smartphone owners who are on a capped data plan will be well-versed in the issues of having a limited amount of data. As smartphones place a great deal of focus on making use of apps, this is sometimes one of the biggest concerns for those on limited data plans. You have just heard about a new app which has become available (while away from a Wi-Fi connection) and you then have to make that decision. To download now and use up some of that precious data allotment or wait until you get home, to work, or anywhere else nearby that has a Wi-Fi connection that you can use to download.
Well, while Google and the Play Store cannot exactly remedy the ability to download apps on limited data, it does seem as though they are looking into ways of making the issue a bit more bearable. Namely, a new feature currently seems to be in testing where a user can defer downloading an app until they are no longer dependent on data. Now of course, the user can simply just try and download the app later on and when on a Wi-Fi signal, but the idea here seems to be that you can check out the app now, instruct Google Play to 'wait for Wi-Fi' and the app will essentially be queued up and ready to automatically commence downloading once you are on Wi-Fi again. Omitting the need to have to return to the Google Play Store at a later time, search again and begin downloading the app.
As mentioned, at the moment this does only seem to be a feature which is in testing and by the looks of it, very limited testing. So chances are that you will not see the feature live on your device. However, it is worth mentioning that if you are seeing the feature working for your Google Play account, the 'wait for Wi-Fi' pages do seem to state that if the feature is cancelled for whatever reason, the downloads might automatically start downloading using your data. Something to keep in mind if the feature is live for you and you are on a limited data plan. You can see examples of both the current download while on data (left) screen and the newly being tested 'Wait for Wi-Fi' (right) screen in the image below.