EngineLink APP OBD2 Reader for iPhone
 

Engine Link - OBD II vehicle monitoring and diagnosis
The reason to start this thread is to: introduce the app, discuss using this app for fuel efficiency purpuse. Here is an screenshot for the app.

EngineLink App BENEFITS
 

* Emission Test.
* See what your car is doing in real-time.
* Read and clear OBD fault codes.
* Display car performance and sensor data.
* Customizable gauges, showing only the data you were interested in
* Top Ranked Car App

How does it connect to the car?

OBDII port
 

All cars and light trucks built and sold in the United States after January 1, 1996 were required to be OBD II equipped.
You can plug a Bluetooth Low Energy adapter or a WIFI adapter to that OBDII port under your vehicle dashboard. The app will talk to it via Bluetooth or WIFI.

So this works with the cheap elm bluetooth adaptors? I have an old iphone 4s i will check it out and let you know! I have a new battery in the mail now.

Bluetooth adapter
 

Do you have a link for your Bluetooth adapter? There are 2 kinds of Bluetooth adapters.
1. For Bluetooth Low Energy Adapter (aka Bluetooth 4.0), it will work right away. Auto configure, auto connect.

2. For Generic Bluetooth ELM327 (Bluetooth 3.1) device: iPhone/iPad has restriction on Bluetooth support (Basically iPhone/iPad/iPod requires BT data device to have a special Apple authentication chip which 99% of the BT adaptors don't have). In order to use standard Bluetooth devices in data mode you need to jailbreak your iPhone. There is a tool in Jailbreak store to manage the Bluetooth. If you have jailbreak iPhone/iPad and that tool installed, you should be able to use Engine Link with the OBD II Bluetooth device.

New Auto ELM327 V1 5 Interface Bluetooth OBD 2 OBDII Car Diagnostic Auto Scanner | eBay

This is the device I have it has worked great with all 5 of my android devices. I do have a jail broken iphone 4s with a dead battery. I got it from a friend I ordered a new battery and after I get it up and running I will try to get it to work. Can you link the other OBD2 device that will work with a stock iphone?

Bluetooth Low Energy Link
 

You can find the Bluetooth Low Energy adapter at ebay by search LELink.

Bluetooth Low Energy Link
 

You can find Bluetooth Low Energy adapter at the outdoor-apps site at Outdoor Apps In The Palm Of Your Hand

At $45 + $5s/h you should just spend the extra $20 and buy an ultra gauge. Torque app is popular because the blue tooth thingys are like $5...