James, I get what you're saying. One thing that I had forgot about was that the 536 has the auto shut off feature that will power the scanner down after a certain amount of time, leaving the mechanical on/off switch in the on position. At least that's what I think happens, as I've never used that particular function on my 536. So that being the case, if it was shut down that way, if the dongle was still "live" as you mentioned, it shouldn't be a big deal at all to bring the scanner back up remotely.
I HIGHLYdoubt the WiFi dongle and/or supporting circuitry is still powered up when the scanner shuts down.
I know there is sleep timer configured in the scanner, the 436HP has a soft switch, not paid a lot of attention to my 536HP as I think I have only used the switch about 3 times!
What would be the bomb is if someone could hack the 536HP so an ignition sense wire can turn the scanner back on. Probably some sort of flip flop might able to wake the scanner up??
The way Uniden should have designed the scanner would have been to utilize the 2 separate power connectors for different purposes.
Coaxial wall wart power input should have allowed the scanner to go into standby with the WiFi running and the scanner should have been capable to remotely powering up and down via the WiFi app.
The 3 pin plug power connector should have been 4 pins, adding an ignition sense wire to wake up the scanner with a user programmable delay of up to 30 seconds after the vehicle is started. This is because standby current would need to be limited to 15-20 mA.
Programmable auto shut down on loss of ignition sense, delay after loss of ignition sense or remote shut off from smart phone App.
Would also be useful for a 12 Volt triggered output for external powered speaker or RF preamp or other devices.
A lot of this would not be too hard or expensive if it was planned into the design, even if there was an interface for an external "box" to address some of these features.
Maybe if I ever get some free time an I am bored I might look into how the power circuitry functions.