This is an example call:

[s,w] = system([IMAGEMAGICK_PATH,'convert ',pwd,'/',outfile,'.png -rotate 90 ',pwd,'/',outfile,'.png']);

This is the error:

error:
dyld: Library not loaded: /opt/local/lib/libtiff.3.dylib
Referenced from: /opt/local/bin/convert
Reason: Incompatible library version: convert requires version 12.0.0 or later, but libtiff.3.dylib provides version 11.0.0

The work around is to replace the Matlab library with the ImageMagick one (only need to do this once and will stay until you upgrade Matlab):

cd /Applications/MATLAB74/bin/maci/   (or wherever your Matlab is installed)
mv libtiff.3.7.1.dylib  libtiff.3.7.1.dylib.MATLAB  (give it a different name)
ln -s /opt/local/lib/libtiff.3.dylib libtiff.3.7.1.dylib  (create a soft link to the Imagemagick library file)

EDIT: This is the much better way to handle this:

setenv('DYLD_LIBRARY_PATH',['/opt/local/lib/:' getenv('DYLD_LIBRARY_PATH')])

java.lang.UnsatisfiedLinkError: no rxtxSerial in java.library.path thrown while loading gnu.io.RXTXCommDriver
??? Error using ==> serial.serial at 57
The serial port object is supported on the Solaris, 32-bit Windows and 32-bit Linux platforms only.

So, to get it successfully working, I downloaded these files: SerialComm.m, SerialComm.mexmac and SerialComm.mexmaci from http://svn.berlios.de/svnroot/repos/osxptb/stable/Psychtoolbox/PsychHardware/.

You can then use code like this:

PORT = 1;
% close (if previously open)
SerialComm( 'close', PORT)
% open
SerialComm('open',PORT,'9600,n,8,1')
% flush the buffers
SerialComm( 'purge', PORT)
% status
SerialComm( 'status', PORT)
% read
STR = SerialComm( 'readl', PORT);
% close
SerialComm( 'close', PORT)

[UPDATE 02 Apr, 2008]: Note, this same code didn't seem to work on a recently purchased Macbook. Good luck.

[UPDATE 27 Mar, 2009]: I see that in Matlab version 7.8.0 (R2009a) if you go to 'serial' in Help docs it now says for Mac OS X and Mac OS X 64 you can use serial('/dev/tty.KeySerial1'); I don't have a way of testing that right now, but it's possible that you don't need to use this third party toolkit anymore. If that's true, please leave a note here.