I finally got around to making a switched power cord for my accessport.
I got an ap a few weeks ago. It’s cool. I started playing with it and I like the average mpg and also the different param’s it can monitor. I don’t know what sucks more though, having a cord and dongle in between your legs, or having to unplug the accessport every time you turn off the car. USB ports can break easily.
I wanted to be able to leave the ap in the car most of the time, and have it turn on/off with the ignition. I also wanted to be able to turn it on/off independently of the car’s ignition. Some dude on iwsti was using a standard spdt relay to do this, which was perfect, doing just about the same thing.
I improved on his idea a little, but tried to keep it simple. It got a little cumbersome though with a relay, the relay plug, and the extra wiring. So I eventually enclosed most of the wiring and the relay in a hobby box.
You can see the usb cord going from top to bottom of this picture. The power, ground, and 3 wires for the switch go out the left side. The relay and harness had to be ‘massaged’ a little to fit 
Cut into the usb cord and get to the red power wire, cut it, splice the ends of the red wires into the relay (pole #'s 87 & 30). I used a mini add-a-circuit for the switched power, run that to the relay (pole#85), ground the relay (pole#86). You get something like below, the ap’s dongle connects to the mini-usb on top of the picture, the ap connects to the usb on the bottom of the pic. I used usb cords I had around the house, which is why it’s 6" long and I’ll use that extension:
I used a mini dpdt switch to get the power options I wanted, it’s wired so in the down position it gets switched power, the center position is off, and the upper position it gets uninterrupted power. Here is the switch done, I used a molex-type connector I had laying around to aid install:
This is about version 3, I’m done. A more oem harness look:
It works like it should, and it’s as proper as I can make it.
The ap can disconnect depending on cord interference, very common. Hasn’t happened to me with a regular cord, but it’s Safe to say the relay, and the extra wire length adds inteference. So I’ll put on a couple extra ferrite cores on it.
I’ll put it in the car tomorrow. Hopefully that will go well.