Guardian Firewall claims to be the first proper firewall app for iOS. It works by routing all the network connections from your iPhone or iPad through a VPN, and then filtering out privacy-invading trackers on Guardian’s own servers.
The idea is that all the heavy lifting is done on those servers, so you don’t have to worry about battery drain, or on the iOS security features that prevent an app from futzing with your internet connection.
Sounds good, but should you trust Guardian Firewall?