What are apps are people using to support GTD on the iPhone?
I use Toodledo. There is a an iphone app, but several other iPhone apps will sync to the Toodledo server. I think the best of these is Appigo Todo. Some people like Remember the Milk. If you use a mac, take a look at Things and Omnifocus.
Would an Ipod Touch also work for these GTD apps? I think it is an Iphone without the phone.
I have a 1G Ipod touch and so far as I have had experience - I have yet to find any app that does not work with the Ipod Touch as does the iPhone; however, any of the web-apps will not work unless you are connected to a wireless connection.
I've tried Things on both the iPhone and my Mac but I personally found it to be too simple. I'd recommend it for someone first starting out with GTD.
I've recently replaced these with Omnifocus after it seemed to be the most popular and I have to say I can see why.
The capture element to the iPhone app is very quick and easy to use which is what you need when you need to grab that thought. I also like how easily the iPhone app is to see what I need to do next, to create projects and next actions and how to mark them as complete.
The app has the ability to be as simple as you need it to be but also to be how complex you want it to be.
The sync function works very well with MobileMe and within seconds everything appears on both the iPhone and the Mac.