If you loose 20-30 PSI "slowly" during a single day, then the PressurePro would definitely save you. In fact, the 20% below "cold initial reading" PSI wouldn't even happen on my Trailer; I punch the "on" and "arrow " buttons every hour or so to see where it is. After going down even 5 PSI, for no obvious reason such as cool-down, I'd have noticed.
But for a REALLY slow leak, everyone checks their tires each morning anyway, right?
I love mine.