I may be able to shed a little light on what you are trying to achieve. I myself am more of a car guy, previously being in the industry for 8 years working at a reputable fab shop building turbo kits alone with a plethora of other stuff we sold. I had the same idea you had at one time for my drag car. It is called a Neptune Tunerview. If your vehicle is not a Honda, I am sure you could still use the display and software in conjunction with a Arduino board connected to your sensors as inputs rather than to a ECU sending signals.
Nope no Honda here, A Lincoln Mark VIII with about 500Hp. The sensors are monitoring things that are not attached to the PCM / ECU.
I'm using the Autometer sensors since I have most them and I have the voltage to pressure scale on my laptop now.
I found a local guy that had 'some' of the stuff I wanted, So heres what I got...
1 Arduino uno SMD (1 month old)
1 proto shield kit (unassembled)
a ziplok bag full of resistors
a ziplock bag half full of ceramic disk caps
about 40 LED's
10 tricolor LED's
2 small breadboards
couple hand fulls of switches
couple hand fulls of pots
couple hand fulls of breadboard jumpers
a 3v 5v 12v dc / 120VAC power supply
a breadboard voltage regulator (not working)
2 16X2 parallel LCD's one backlit one not
and a bag of misc. stuff (chips, sockets, sensors, etc)that I haven't gone through yet.
all for $100 and a promise to post the final sketch and to show him the project when finished.
I'd say about 90% of the stuff hasn't been used so its my turn to abuse it.
I decided to go head long into getting something work so I'm in the middle of troubleshooting the LCD 'Hello world' example. I've got it wired up and my laptop is talking to the uno now, but its not showing the text 'hello world' so i'm off to the tutorials to figure it out what i'm missing. I've been at this for about 3 hours so I feel I'm at a good place.
nice site already in my bookmarks