Late to the party, once again. Just discovered Debug Console in iPhone while looking through the Safari Developer Library and stumbling upon Safari on iPhone Tools:

Safari on iPhone OS provides a debug console which reports messages, coding errors, warnings, and tips. In the iPhone Simulator or on iPhone or iPod touch, launch the Settings application. Navigate to “Safari”, then to “Developer” and toggle the “Debug Console” switch to “ON”.

This is going to help. A lot.