A company named vimov is attempting to address this problem with an update to its product for the iPhone and iPod touch, called iSimulate, that now allows developers to pipe accelerometer, multitouch, compass, and GPS data from the iPhone into the iPad simulator. Until now, developers had to make educated guesses based on past iPhone development experience, but iSimulate aims to help make the experience a little more painless.
Setup is pretty simple, according to one developer we spoke to: you only need to add a library into an existing iPad project and then connect to the simulator from the iSimulate client on your iPhone or iPod touch. The same developer, however, informed us that the system was far from perfect. Apparently, it's virtually impossible to know where you are touching in the simulator until you touch the screen on the iPhone; this is because the application isn't running on the phone, and instead, only a diagnostic screen is visible. Additionally, the response speed of the simulator leaves something to be desired.
Still, he said the GPS and accelerometer support could be very useful in development, especially since there's no other way to test this except with an iPhone or iPod touch. If Apple starts taking application submissions prior to the availability of iPad, devs are going to have to rely on applications like this to ensure their applications work properly at launch.
Source: Arstechnica.com