VPN Leak Detection?

Hi everyone,

I'm playing around with building a tool I've wanted to attempt to make for a while: a small app that lets you know when your VPN has leaked or silently failed.

I'm curious if anyone knows of an existing tool. I know many consumer VPNs have kill switches built in to stop network connections when the VPN fails or will alert you when the VPN is off. I don't know of any that are checking for leaks or for bypasses like TunnelVision.

I'm also able to find a lot of websites that let you check your privacy signature and tell you if there's a VPN leak, but I'm not able to find any that function as a service to make it easier on the user.

Thanks in advance for your thoughts!