I've also created a controller app for the iPhone/iPod touch called "Squash Controller". It was just posted to iTunes yesterday. It doesn't offer all the features of iPeng, but I really wrote it for myself and decided to make it available to the world anyway.
For those of you interested in trying it, I can give out promotional codes for a free download for the first ten or so people who contact me. You'll have to be from the United States, though, I'm afraid. It's a limitation of iTunes. I think anyone can buy it, but the promotional codes only work in the U.S. store.
-Rob