We recently deployed a restrictive web filtering policy with Cisco Umbrella DNS filtering using Cisco Security Connector for iPhone with Meraki MDM. There are approximately ~28 application categories you can block with Umbrella at the time of this writing. The main focus was to limit Ad Tracking.
Category Descriptions
Ad Publishing—Applications that enable publishers and ad networks to manage ad serving and trafficking.
After implementation we noticed that iPhone battery life was cut almost in half. Phone batteries were drained by the middle of the day. Investigations into what was being blocked through Umbrella reporting showed a high number of Ad Publishing DNS request were being blocked. We selectively allowed certain applications which restored battery life to normal. While we did not do packet captures to determine the number of DNS rerequest, we suspect that the iPhone application continually tried to retry the failed DNS request causing battery life to drain.
See a complete list of Cisco Umbrella Application Categories.