Thumbs up!
Very pleasantly how stable it was on my Model 3. Experimented with it doing multiple applications while simultaneously playing audio and only managed to crash it twice. That said one of the crashes was a restart and crash again loop. The only way to stop that was to dig into the application list on my phone and kill the process. Not something possible to do safely while driving.
Worked well with my midrange Pixel 5a. My guess would be you wouldn't want a much slower phone. Between the application, the hotspot and the GPS navigation it's likely going to draw some current from the battery. No wireless charging on the 5a, but my guess is if your wireless charging is under 1A to 1.5A you are likely going to slowly drain your battery.
Not the application's fault, but the starting process is a bit of a pain in the neck. You've got to start the hotspot and for me I now have to tell the car to switch from my home WiFi to the hotspot. After that the application should take over. Realistically I don't think I'd use it very much unless I was taking a trip and wanted access to something like Waze or ABRP.
That said it's definitely worth the USD$5.00 for the application.