<p>I'd like to log the <em>call trace</em> during certain points, like failed assertions, or uncaught exceptions.</p>

This
pretty much tells you what to do.
Essentially you need to set up the applications exception handling to log, something like:
```
```
#import <ExceptionHandling/NSExceptionHandler.h>

[[NSExceptionHandler defaultExceptionHandler] 
                  setExceptionHandlingMask: NSLogUncaughtExceptionMask | 
                                            NSLogUncaughtSystemExceptionMask | 
                                            NSLogUncaughtRuntimeErrorMask]
```
```