As everyone knows, Apple blocks most paths to get data into the iPhone from a MCU via Serial or bluetooth. After trying many apparent solutions I decided HID was a simple way to do it. A new App on the Appstore called Magic Montor X uses the HID profile to send data from your Arduino or any other RX/TX device to the iPhone. Basically HID emulates a keyboard so it reads the incoming data in ASCII format. HID bluetooth is portable so you're not stuck with Ethernet Shield. It is cheap, you can add a HID bluetooth module for about $17 or even cheaper if you know how to implement HID profiles.
You can send up to 7 different data messages to the iphone and each will appear in a different "Monitor" Window. There are also 6 LED's you can turn ON or OFF. All this data will update each loop of your sketch.
You can customise the display to show 1 to 6 Data windows and name the units for each window.
The simplest solution I found is using roving Networks RN-42 and simply connecting it to RX/TX. It pairs seamlessly with iPhone and then you can just serial.Print data to the phone.
Control characters are used to get the correct data to the intended data window.
It is wireless and so much better than an LCD display.
Any questions, let me knowhttps://itunes.apple.com/us/app/magic-monitorx/id583180732?mt=8