@Marta - this particular entry is for 12a. but http://www.mathworks.com/matlabcentral/fileexchange/40312 is for 13a and beyond. you can read more information here:
@Phillip - Mac support for this arduino support from simulink was added in R2013b... you can use this entry to initiate installation, but you will need 13b for Mac support.
I'm using 2012a for Mac OS x on 10.8 and when I type
targetinstaller, it pulls up the Target Installer window, but then when I select Internet as the option, I get:
"Select a Target
does not contain a valid support package. Please specify a folder that contains a valid support package and try again."
If I download the submission into my downloads folder and use the 'Folder' option and point it to the folder 'rtt_arduinomega2560_r2012a_v1_0' it also complains and says it is not a valid package.