NoRoot Firewall app (I'm not affiliated). I must have brought it up in every Android security related post in HN that I've came across.

I use it on all my Android devices. I block all traffic in most apps.

Some Android phones allow you to allow/block Data and/or WiFi separately. My Samsung 4G tablet doesn't allow me to switch off Data or WiFi for some apps, especially the system ones.

This is where NoRoot Firewall does all its good work. It has Global Block list (all ads/trackers go there) and for each app I individually block or allow certain IPs.

So if "Samsung Keyboard" app wants to send your typing home, you block Data/WiFi and leave it trying :)