So I've had the iPhone for a bit over a month now. Liking it quite a bit (even if the Facebook app doesn't let me access Tiny Adventures! WotC, make me a Tiny Adventures app!).
I spent a few hours last week putting together some ringtones, which is stupidly easy. Since I'd just gotten a cd of SF movie themes out of the library, it was even geekier than it needed to be.
I have tried a variety of apps for the iPhone. They make it stupidly easy to get them, including a link to the App store with your phone.
The one that's probably going to get the most use is Dicenomicon.
Rentagurkha, before he was consumed by work and impending fatherhood, mentioned it a while back, and
nottheterritory reminded me about it when I mentioned I needed something better than the dicebag utility I'd previously tried.
Dicenomicon is a very strong program. It does a lot of dice types; without doing anything you get the standard TSR era polyhedral run on the front screen, d4-d%. They have a variety of other rolls, including Champions damage dice for normal attacks and killing attacks.
You can program in commonly used dice rolls. For example, for Lacklow I've programmed it to do a to hit for regular and flanking attacks with both his regular attacks and his encounter attacks. I haven't programmed the dailies in yet. It calculated the damage at the same time as it rolls the to hit rolls, and on flanking attacks, it also calculates sneak attack damage.
I think there may be an option for calculating criticals on there as well, but I am haven't found it yet.
It does dice for ST, for Feng Shui, and for Shadowrun and GURPS. And they'd upgrading it all the time.
Just so you don't miss out on tendon degenration, you can roll the dice by shaking your iPhone in addition to pressing a button.
All in all, though, it's a great program. Well worth the three dollars.