A company called Fresh Design Base have just released a pretty decent 2D CAD app on the iPhone/iTouch called SitePAD.
Its a bit tricky to get to grips with but looks promising. Theres some sort of cloud computing file transfer system to allow you to take your drawing in and out of your desktop CAD app. Looks like it has real potential for those of you who work out in the field or on 'site'. Their website has a bit more info,
www.sitepad.co.uk.
Word is it will work on the iPad using screen doubling mode, but there is a native iPad version in the pipeline.
Might be the first step to mobile and touch based CAD'ing!?