I'm thinking of using Ray Wenderlichs tutorial for a Ethernet-arduino project as well. (But that will be during summerholidays i guess)
You could do the following starting from Ray's tutorial:
- add a slider to the Storyboard
- create an IBaction (ctrl drag from slider to .m file) & add a touch up outside routine or a ValueChanged routine:
- multiply the value of the slider x 255
- convert this integer into a string
- add this string to: --- NSURL *url = [NSURL URLWithString:@"http://10.0.0.25/
Modify your arduino code so that the value of the added string is the value of a PWM signal at the output connected to the led.
I'm still a rooky myself in Xcode programming, but these could be basic steps. Also, there is a lot to find on stackoverflow.com on general Xcode programming.