These Bluetooth devices like this particular one are really unnecessary and a bit of a gimmick really.
I have a volt meter built into my Bel radar detector and have that displayed all the time so I’m monitoring my charging system all the time while I’m riding.
As far as testing my battery, I have a 1 year old Yuasa installed and have it on a battery tender whenever the bike is parked, so I know it’s always at optimum charge capacity.
If I bought one of these it would be a toy to play with, I’d be bored with it in no time, and it would be a waste of money for me, I’ve been down this road many times lol.