You got your Mac, you got your iPhone and iPad, and you installed XCode. So let's build the one-million-dollar app, right? No, hold a second. Because before you even write your first line of code, have your users test your app.
You have no Mac, you have no iPhone or iPad? But you have a great idea for an app? Then let's have your users test your idea.
Am I making fun of you? No, because before you write code and an give your users a running app, you can create astonishingly real looking mockups of your app, that don't feel like a mockup. And that you can give users to test and give feedback. They help you to avoid a miserable failure because of all the time and money spent for coding an app that misses your target audiences' needs.
The following tools will help you - developer, solution manager, guy with a great idea - build a life-like looking prototype of your app and accelerate development of your future killer app. Depending on what app you are eyeing, these tools are for you.
This tool allows you to bring your iPhone mockup on your iPhone. Sufficient to get a good first impression for the layout, navigation through links and look & feel. Sure you can't have everything (animation), but hey, that's what's your task when finally programming the app
Stencil kits are collections of common graphical elements like buttons, headers, sliders, dials etc. that you find in a variety of iPhone/iPad apps. Websites like Graffletopia offer a growing number iPhone and iPad templates for download, Yahoo! besides the templates also design tools to create your own stencils. It just doesn't give your prototype the real feeling of your future app, you will use those stencils later in your life app.
Amir Khella provides a treasure trove of tools and how-tos for creating interactive iPhone or iPad mockups in 30(!) minutes. Just watch his videos and you'll be amazed how easy it is.
While Apple's iPhone/iPad SDK Xcode comes with simulators for both the iPhone and iPad, many folks who want to develop apps might not own Apple hardware. The still can run simulators that are available for PC. MobiOne for the iPhone, iPadgeek for the - surprise - iPad and Adobe AIR based simulators are available.
As Etay Gafni, former SAP colleague and now founder and CEO of BrightAct, said "Nobody wants to write specs and even fewer people want to read them", give the people a screen shot or even better a video to see what your app does or should do. Be it that you as solution manager or guy with a great idea want to tell your developers how the app should be or if you as developer want to show your customer what your app does, make a video. The simple but free SimCap from Apple or the not free but with all bells and whistles iShow U HD screen capture tools will help you with that.
We keep an updated list of tools in our SAP Mobile wiki. Keep checking it out.