I think I finally understand what ewodzien is asking. There is actually another state: Empeg present in sled.

ewodzien wants an accessory powered up when the Empeg is present and in standby mode; and powered down when the Empeg isn't present or has no power.
The accessory will be connected to the Empeg via the sled (so the accessory will still be connected to the sled wiring when the Empeg is removed).

The problem is that the only power output provided by the Empeg (the Ant remote), is switched off when the Empeg is in standby.

You could build a circuit to test for the difference between connection to ground and high impedence on the Ant line. This effectively has three states:

~12v dc - Empeg in "On" mode
0v - Empeg in "Standby" mode or unpowered
High Impedence - Empeg not in sled.

If the circuit were powered from the power line (on the sled, this is the yellow wire that goes through the inline fuse) rather than its own power source, the logic out of your high impedence detector would look like this:

Low - Empeg in "On" or "Standby" mode (or unpowered)
High - Empeg not in sled.

So if you want the accessory powered in "On" and "Standby" modes, you just invert the output:

High - Empeg in "On" or "Standby" mode
Low - Empeg not in sled (or unpowered)

If you want the accessory powered in "Standby" mode only, invert the output then AND it with the inverted Ant. power output.

[edited: corrected detector logic]