ya teh audio jack would work great.... you could slap that on the dash in plain site and no one would ever know! thats good thinking keep it up!
get creative and it can turn out great...

afew more ideas is get a cheap set of RCA wires and use them with a simply Y adaptor to connect the 2 paths to power the fuel pump or what not.
you could even hardwire your cig lighter plug to power the fuel pump or a relay to power the fuel pump. you can easily find a cig lighter plug and such to wire up.
you could even use a factory fog light switch or even the headlight switch if you wire up a relay to the fuel pump and use the positive headlight power wire to activate the relay. thats a nice hidden kill switch... a thief is not going to turn the headlights on at night when trying to steal your car.LOL
could even wire up a relay to your power window switch to only have power when you have that tiny switch set to left or right.... youd have to cut up your switch but lets face it you really dont adjust the mirrors much do you? but if you do you can always get another switch from the junk yard and just slap the switch under the dash so you can still get to it.
i could go on but id name everything that is on the car that uses power.

thats the wonderfull world of custom wiring... if your unfamiliar with wire wiring and relays... PLEASE READ http://www.the12volt.com/relays/relays.asp
they have TONS of ways to wire up relays to do all kinds of things!
this is the relay diagram that you will typically use.
http://www.the12volt.com/12voltimages/addremacc.gif

this way is good if you want to just hit a momentary switch to activate the fuel pump.
http://www.the12volt.com/12voltimage...ntconstant.gif
http://www.the12volt.com/relays/page5.asp#mtc

 

i just added a quick disconnect steering wheel, gonna have to bring there own if they steal it and also as soon as it turns on my car pc turns the gps on so i can track it anywhere from any pc, its a cheap lojack

 

My uncle had a remote key kill switch incase he was car jacked while waiting at a stop light. I talked to him and he said he had a Remote Starter installed in reverse so it killed the car until pushed again. See if you can find someone that could do it for you. Ive searched for my car so far no one around where i live knows how to do it. Just keep lookin