What is the name of the tool?

Meters are visual and distracting. I had meters on amps before. The ones with no meters usually sound better.

I prefer music following lights.

russ69 is all that.

Unless you can calibrate them, they’re useless.
If can you need a known resistance and a scope to allow them to tell you next to nothing.

You will get better use out of that KILL A WATT.

You might also read up on decibels and power. 

Sansui made a light display "watt" meter. I had one in the 70s hooked to my AU 717.

Meters on amps aren’t necessary or really useful but they can be pretty 

Ampzilla with decade meters-4 orders of magnitude. VERY useful for training oneself, lower decade readings quite sensitive. I am a scientist, these things fascinate me.