Do you have any case studies showing what the actual overhead is? I love the idea but would worry about negatively impacting the customer experience.
CPU-wise, our SDK adds up to 2% overhead to normal UIEvent-handling. This is with frantic and constant user input - in practice the overhead is much less. Network-wise, we batch user activity and by default make a network request every 5-10 seconds. We'll expose a config variable so devs can tune this frequency on a per-app basis.
On top of that, burning 2% overhead on UIEvent handling (which also impacts battery).
What a waste for something that users don't actually want you to be doing in the first place.