Here's an excerpt, mentioning some apps from fellow developers here...
Ive also been playing with the Pogo stylus from Ten One Design (www.tenonedesign.com). Its not an app, but it has made my screen taps more accurate and really helped me improve my scores on fast-paced action games like Squares2.) They also offer the SoundClip, a plastic clip-on that improves your audio experience with handheld games such as Wooden Labyrinth 3D. The problem is that users hands can cover the downward-facing speakers on the iPhone and iPod touch. SoundClip redirects the audio towards the user, where it belongs.
http://tinyurl.com/cwq6u2
Ive also been playing with the Pogo stylus from Ten One Design (www.tenonedesign.com). Its not an app, but it has made my screen taps more accurate and really helped me improve my scores on fast-paced action games like Squares2.) They also offer the SoundClip, a plastic clip-on that improves your audio experience with handheld games such as Wooden Labyrinth 3D. The problem is that users hands can cover the downward-facing speakers on the iPhone and iPod touch. SoundClip redirects the audio towards the user, where it belongs.
http://tinyurl.com/cwq6u2