We've released a new app called Fialer!

Fialer is a standalone, drop-in dialer replacement app that will become the fastest and easiest way to utilize dialer codes to switch networks for Google Fi users! With Fialer there is not need to be rooted or enable Accessibility. In addition to making switching networks faster and easier, Fialer also gives you more control over to which network you are connected depending on when/where you are by executing dialer codes in the background! You can read more HERE.

Fialer integration is FREE for Signal Spy Pro users!

The first link is to opt in into the beta and second is to download the app (you might need to wait a couple minutes between using the two)
https://play.google.com/apps/testing/com.novvia.fialer.sse

https://play.google.com/store/apps/details?id=com.novvia.fialer.sse