Long range active RFID

Yes I know there's a bazillion designs for short range ( a few inches) RFID everywhere you look,but I need something with a range of up to about 5 metres or so. I'm trying to make a PKE (Passive Keyless Entry) system for my car that locks it when I walk away and unlocks it when I walk back to it,all without having to press any buttons.
Normal PKE systems use a very low power LF transmitter at 125 kHz that effectively push the arm/lock button for you when the remote fob stops receiving the LF signal and do the same to the unlock/disarm button when it picks it up again.I've even still got the 125 kHz transmitter modules that came with the crap Chinese PKE alarms that all went wrong within a month or so.

Sooooooooooo...............what are the options for using an Arduino for something like this? All it needs to do is to provide a +ve pulse to arm an existing 2-1 upgrade alarm and another +ve pulse on another wire to disarm the alarm.

Bump.Has anyone got any ideas on this subject please?

HI THERE I WAS WONDERING IF YOU HAVE GOTTEN ANYWHERE WITH YOUR PROJECT, I WANT TO DO THE EXACT SAME THING BUT ALSO DO A PUSH TO START BUTTON ON MY CAR.
I HAVE AN OLD 66 MUSTANG SO IT WONT BE THAT HARD TO PASS THE ORIGINAL KEY TUMBLER BUT JUST DONT KNOW WHERE TO REALLY START WITH THE ARDUINO.

No sorry,but due to a complete lack of any replies I didn't get anywhere with this.I have made a single button start/stop system for my own car though,not an Arduino but just some old fashioned latching relays if you're interested?