Always on

Currently looking at the PDM25+ for use in a road car (classic with engine transplant). Obviously it has many great features and getting rid of all the relays and fuses is a big plus, but how do you control or use anything that doesn't require the ignition to be on? (I believe the MOT doesn't require the horn to work with the ignition off but most cars seem to anyway).

I guess items like alarms and remote keyless entry will have to be its own system and fused? Thought it would be good to connect the door locks into the PDM and potentially use a CAN message from an alarm (or other device?!?) to unlock and "enable" the car? Does the Ignition feed completely kill the power or does it just sleep? Could the USB be always in to keep the processor on but limited function (like a sleep/ wake state) ? Can anything be controlled with just the usb? assuming its solely for setup / config. I ask really as part of the integration would be to have the PDM control the indicators/lights/ fans / electric water pumps etc. so using any of this after the car is "off" would require the PDM to be on all the time or at least for a set time after ignition is off.

i.e. key out, ignition off, electric pump on and fan on until the engine cools to a suitable level. or Lock car and indicators flash. Just nice features like that but is seems either PDM on all the time, or bypass circuits/timers and fuses to allow this kind of thing (and defeat the purpose of the PDM)? Ending up with a PDM power timer? 😣

Thoughts? 😁

Ed.