There are a lot of reports (e.g., ars technica) that the iPhone 4 has both better and worse reception than previous iPhones depending on how you hold it. Here’s a way to address it through a proposed application.
The newest iPhone comes with a number of internal sensors – proximity, accelerometer, and compass among them. Some developer with access to the iPhone 4 SDK should build an app that uses these sensors along with the signal strength metering output to enable users to train themselves to hold the phone optimally (otherwise impossible when you’re yelling, “Do you hear me now?” into the phone). The app could vibrate the phone or provide an audible indicator of optimal signal strength. --Dennis