Aside from the iPint virtual beer, this may be the most appropriate iPhone app for geezers. The iPhone 3G has hundreds of apps, but if your heart gets racing over the newest MacBook Pro, the iPhone Heart Monitor will give you a heads up that a call to 911 may be in order.
To use the iPhone Heart Monitor, you hold the iPhone to your heart, and the mic broadcasts your heartbeat and monitors the rate. I don't know why this wouldn't be fun for other parts of your body that are capable of making noises too. Is there a market for the iFart or the iBelch?