Maybe we'll get lucky and Uniden will make a 536 detachable face with ignition sensing and a capacitor that lets it shut down safely in a mobile environment.
I have raised this issue and most of the hooks may already be in the hardware??
The 3 pin power connection on the 536HP has a dash light monitor/display dimmer input.
There are software hooks to adjust the display dimmer behavior so it may be feasible to use the dash light input as an ignition sense input?
Delay power up on ignition sense and proper power down on loss of ignition sense.
The radio already has a power off timer configured in the firmware, so it there is a way to modify the firmware to follow the ignition sense, then boom, you have your problem solved!
Again, assuming the hooks are all there, which appears they may be. This means probably getting rid of the automatic dimming while monitoring the dashlights.
But another option is to use the real time clock as a way to automatically dim the display. Sunrise and Sunset is 100% predictable depending on your location. A look up table can be used to predict the sunrise and sunset assuming there is enough memory. This could be something that is accessed on the SD card and a small table be cached in the scanner.
Lots of ideas, but at the end of the day the primary purpose of the radio is to scan and as I last recall we are STILL waiting on features that were promised 1st Quarter 2014 which will very soon be 3, yes 3 years!!
There has been some movement, but not enough IMHO regarding the Apps, Features and my take on what Uniden promised was the ability to remotely access the scanner using the App from anywhere!!! This all handled internally by Uniden servers and software, not requiring every end user to be an IT specialist to configure their own VPN.