Thanks for the recommendation. As of this evening I deployed my own design for a security system. It is based on ESP8266’s and a 4g cell module. It is sending texts on state changes, and Low Battery levels. I can also remotely poll it by sending a SMS to it and get a status report. I had designed one for my RV and just migrated it over to my condo.
Hey guys! Sorry I’m a bit late to the conversation but I was also having this issue having recently moved to a Mobile Broadband internet plan. My hub seemed to be sending and receiving about 1GB per day. I only had a door sensor… so I did some digging and may have found a solution. I’ve only tested this for 1 day but it looks promising
I downloaded the Plume app that connects to the hub. Go to settings and enable “Privacy mode ON” or something similar. This will disable the “Safe browsing” settings. After 1 day of testing this, my data usage dropped from 1GB per day to 6MB!
As I said, 1 day test. Will continue monitoring in case something else caused the drop in usage. FYI I haven’t changed anything in my setup, and wasn’t really focussed on any alerts or anything. This was just a solution on a whim thing!
Please give it a go and see how you go 
I think the app is now called HomePass FYI