On Bulbapedia, it's stated that "An Internet connection is required" and "unplayable during server maintenance",
meaning it's server based, so highly unlikely that it's hackable.
What that means is, pretty much almost any other interaction, and generator or coins/jewels, rng factor, is all handled and sent out from server.
(which is why you can't play when server is offline)
So lets say, if you try to spend Jewels, its not "from your save on your phone", but rather "deducted from the data on server".
I doubt those values can be hacked easily.
I don't know of much [or rather, any] server-based mobile games being hackable from a coin/in-game-currency generator perspective..
I wish we could be more help regarding this, but until I'm told there's any form of progress relating to this, I'm locking this thread.