well, wiring in the turbo timer is pretty easy if you get the harness for it. now having an aftermarket alarm system work with the timer could be a different story dependibg on how the alarm activates. the alarm i had in my old truck would arm itself 30 seconds after it sensed a power loss on a certain wire, if the alarm you have does that then it is a simple matter of hooking that wire to the right spot, your alarm installer should be able to do it with no problems provide the turbo timer is in the car when he hooks up the alarm. but if your alarm activates like the alpine alarm that i have in my supra, it activates when it senses a power loss AND a door opening and closing after the power loss, it takes a little more to make it work. what i had to do on mine was install a timer relay that activated when the car died that cycled the door switch to simulate the door opening and closing.
I've got the Code Alarm on mine and the HKS TT-V type 0 on mine. The code alarm will activate itself after it senses the power loss of 60 seconds. I made the mistake of having the shop do the alarm first and THEN buying the turbo timer. Had to go back to the shop afterwards. The alarm will not activate itself now, until the timer has completely killed the car. Only problem is the Code Alarm does not lock the doors unless you arm the alarm yourself. So I have to lock the doors when I get out, but other than that it works great.