Can I manually re-calibrate the iPhone 4 compass? My iPhone 4's compass is off to a significant enough degree that it's annoying... is there any way to manually re-calibrate the compass?

I have, of course, done the "figure 8" (whatever action that was supposed to elicit) when I first set up the phone, and again whenever the phone prompts me to (which is very rare).  What I'm looking for is a setting/menu/option by which I can call up that re-calibration interface, instead of waiting for it to prompt me.
There is no setting in the standard iOS that allows this. The easiest way to bring that recalibration screen back up is to briefly put a magnet near your phone.