Create a litte iPhone application that lets users insert/see issue, see task.
I agree with Brian - in the North American "non-consumer" market, defacto platform standards are important, as evidenced by Wintel domination of the PC-based client/server architecture. But the next decade may see the mobile architectures overshadow the all enterprise IT that exists today (it seems inevitable in raw number terms). Here the iOS platform (iPhone-to-iPad) is mostly considered a consumer platform which leaves Android as the other 'hot' platform and is seemingly more IT-like (lots-o-development appeal/options/etc.). From all this admittedly unscientific empirical evidence, I'd advocate for an early priority to be given to the Android platform over iPhone for Teamwork's likely users?!?!?! - (sorry Blackberry and WebOS users - a famous hockey player once said "you have to skate to where the puck is "going to be," not where it is now!)
I agree a mobile application for collaboration tools is becoming essential. That being said more of our staff have Android handsets than iPhones so I would prefer and suggest that Teamwork starts with an Android application. Even in the States there are more Android handsets now and if you start to look world wide the latest figures I have read suggest that 90% of smart phones now run Android.