Using SlotCount Digi as a Slotcar lap counter with color detection is okay.
But, as the smartphone device doing the detection has the track in view it may not be easy for everybody driving a race car to find out whats going on in the race.
So this is where this App comes into play.
It's meant to be used on a second Android device, favorably a tablet which is placed near the track where everybody can see it.
When the counting device is ready, just start the monitor device, they will automatically connect via Wifi-Direct.
Then, during a race, the counting device will send each event (leading car, fastest lap) to the monitor device where it is displayed.
Thats not all, the monitor App can remote-control the counting App so you can start races from the monitor App.
It is possible to start and stop calibration sessions from the monitor App.
Using the Pro version it is even possible to edit the car list in the monitor App which is quite convenient.