Signal Info is a free, ad-free Android app developed by MBMC, designed to help Project Fi and Google Fi users keep track of their network connectivity. It can display which network you're connected to (WiFi, Sprint, T-Mobile, US Cellular), and at which speed (2G, 3G, 4G, 5G, etc.). The app is Open Source, and contributions are welcome.

Signal Info records events like airplane mode on/off, phone on/off, WiFi on/off, connected to WiFi, connected to cell service, and cell service speed change. It also has a 1x1 widget to display your current connectivity, and a 4x1 widget to switch carriers from your home screen. You can also export/import your database.

The app also supports day/night mode, which is a nice touch. Notifications are triggered for any WiFi, cell, or disconnect event, making it easy to keep track of your network connectivity. Overall, Signal Info is a handy tool for Project Fi and Google Fi users who want to stay on top of their network connections.