Try an iPhone-optimized Web app: Simple Shopping List. (Best viewed with Safari.)
onetrip.org
onetrip.org
Anyhow, I tried the app out, and I can't decide if it's really useful.
I think it is pretty smart. I think I will try something similar in my mobile applications.
If most mobile browsers' support for javascript is limited or nonexistent, then it makes sense to optimize for Safari, since iPhone users will be the only ones able to use it anyway.
Kidding aside, I still think my shopping list app is better in that you don't use the phone to input the list: