Phono

Phono shows the operator logo in the status bar.
It also provides information about the telephone network and roaming info, signal strength, data network with its state of the connection, the hardware and the operating system of the device.
There are currently supported approximately 400 telephone operators (including MVNO) in 46 countries around the world.
On some devices the signal strength may not work exactly for reasons independent of Phono.
Refer to the home for bug & supported operators

Some feedback:
"Love it I've been using this on Project Fi for a few months. Very informative and very helpful."

"Great for Project Fi Showing the currently connected carrier logo is the most unique feature of Phono, which in high demand by Project Fi (Google carrier) customers. I found no other app that does logo in status bar at top. Maybe Project Fi will some day provide this feature."

"love this app specially with Project Fi the icon on status bar is really helpful to know which provider (Sprint/T-mobile) I am connected to......"