How to get user gameplay data for testing?

How can I send myself back testing data from players? It’s for an iOS game. I assume there’s some method to submit this information via the web in the background when they’re playing, but I don’t know where to start (or if it’s even possible using Unity).

Yes, you can use the WWW class to call your server. If you use the WWWForm class then you can send arbitrary data to your server. A different approach might be to use an analytics service using a plugin.