To reduce power consumption to an absolute minimum, the unit powers off totally, with a drain of ~1mA - just running the power control PIC. This can be programmed using ioctls on /dev/empeg_power to power up the entire system even when the accessory signal isn't present (ie, car not running) - the power up time can be set in 15 second increments up to 10 minutes. If the main cpu is powered up with ACC inactive, a different bootcode (at 0xc000 in the flash as opposed to 0xe000) is called, allowing the kernel to be called with different options.
Currently, the software doesn't do a lot with this; however the idea is to power up the main system (minus HDDs) on these watchdog powerups enough to check for presence of a wireless link & if present to do a full powerup. This way, you reduce the average current needed for the periodic wakeup (maybe 5 seconds of full-power runtime (no HDDs, so maybe 200mA) every 5 minutes). You'd use the amp control line to power up the wireless adaptor too.
It's not really designed for constant-on streaming from car to house (this would run down your battery, though less than leaving a light on!) more for periodic updates. Eg, packaged news delivery arrives via cable modem and gets downloaded to the car into a special playlist for you to listen to on the way to work.
Hugo