VPN/Sentry

Virtual private network with firewall
Features
Encrypt all the internet traffic leaving your device
Allow or block internet traffic per app or address
Simple to use while still offering advanced features
Encrypting internet traffic can help to:

prevent man-in-the-middle attacks
protect against security flaws, like KRACK Attacks
increase your privacy by preventing monitoring, surveillance, etc
Blocking access to the internet can help to:

reduce data usage
save on battery usage
increase your privacy
VPN/Sentry is designed for minimum battery usage and maximum network speed. It does not require root permissions.

VPN/Sentry supports all IP protocols. You'll even have IPv6 connectivity when you normally don't have.

There is a free data allowance of 10 MB per day to try the app. Unlimited data usage is available with a subscription.