I have a mobile app on both iOS and Android, and a key thing I need to start reliably measuring is the number of users subscribed to certain feeds that they can access within the app. I've tried Google Analytics in the past, creating segments based on an event with the feed URL as the label - but they do such heavy sampling of their events that GA has essentially become a random number generator for me.
I'd like to replace this with my own API on my own server that the app pings, so that it can log the number of users in each group. However, there's a ton of stuff that Google Analytics does out of the box, such as online caching of events until the user has an internet connection and so on, that I really don't want to have to implement from scratch. Does anybody know of any (ideally cross-platform) open source libraries that provide a generic analytics framework where I can just plug in my own API?