Apex , i went this road , i got the final answer from Alp :

'' sorry, relays are not yet supported. We constantly work on new updates and functionality extensions, as you probably are aware of. Stay tuned for our newsletters, latest news are usually updated monthly.

Have a great day!
Your ALPriority Support team
--
AL Sales - Croatia
Radikal d.o.o. - J. Mise 8, HR - 10360 Sesvete
Mob: +385 91 446 6657
E-mail: info@alpriority.com
Web: www.alg9.com, www.alpriority.com ''

This is not to say a kill is un-doable , but definitively not by triggering a relay using signal from blue\green wire.
I tried with a micro relay rated 3 volts ...not enough push .




Quote Originally Posted by ApexOnYou View Post
Think of the diode as an electronic check valve - flow is only permitted one way. If the ALP mute wire is in fact outputting 5v at standby (I don't recall what mine was doing) and ground when triggered a diode will block the 5v from reaching the radio circuit while still allowing the circuit to ground on activation. There's probably a better explanation of this on www.the12volt.com

You can most certainly trigger relays from the ALP outputs though. You only need a few mA of current for a positive trigger and a ground for a negative trigger relay setup. Not saying OP should or shouldn't interfere with the cars brake circuit, just clarifying on the relay topic.