I don't have an iPad but using Apple's simulator I have created an iPad version of my Thunder Clap app for the iPhone / iPod Touch… Here is the description:

Following the success of Thunder Clap on the iPhone and iPod Touch, here is Thunder Clap HD built specifically for the iPad.

Thunder Clap HD is simple to use utility to calculate the distance to a storm based on the time elapsed between the lightning and the thunder. When you see the lightning: hit the 'Lightning' button, then when you hear the thunder: hit the 'Thunder' button. The distance to the storm will be shown.

The iPad version has some new extras including higher resolution graphics, full rotation support (it does matter how you are holding your iPad) and an Information Center with some notes about the nature of Thunder and Lighting and a bit about Benjamin Franklin.