When you live in Washington DC, you go out to eat a lot. There are so many great restaurants and eateries. Inevitably, the dinner bill comes and everyone sits around trying to figure out how much tip they should add on.
The problem is now solved with my iPhone. With the Web app Tipr (http://www.tipr.mobi), you just enter the dollar amount, the percentage of tip you want to give, and it will say how much tip you should pay. This is all done in an iPhone optimized environment.
I will be using this app.
Oatmeal Stout - Justin Thorp's blog 
I’m glad you like Tipr. I built it as a tool for myself last Wednesday night, but thought the rest of the world might like it too. If you have any suggestions, please let me know.
Works on my WM5 Motorola Q too…
Though, I may have to play Justin on this and say, “If you really want accessibility and usability for this you should be working not just for iPhone standards, but for general mobile standards as well.”
The 320px resolution is just slightly wide for me.
And I’m a jerk. 🙂
@Nate: It should enlarge & contract based on the browser width. I actually have a Treo 650, so don’t even get the gorgeous CSS layouts and standards-compliance granted by Safari.
At this point in time, mobile development is so fractured. It’s really hard to get a decent-looking design out there. It’s all about simplicity right now. And, to me, simplicity means functional; it doesn’t have to be pretty… it just has to work.
Brilliant!