They even use a Mac, so the instructions will work for you.
+
They even use a Mac, so the instructions will work for you. However, one thing to note is that the Wii doesn't have HDMI, but it does have composite (and component video). I definitely also recommend the Elgato eyeTV products. They also state how well their products will work with consoles in their support pages:
EyeTV Hybrid USA 09: [http://support.elgato.com/index.php?languageid=1&group=englishdefault&_m=knowledgebase&_a=viewarticle&parentcategoryid=1&kbarticleid=1063|http://support.elgato.com/index.php?languageid=1&group=englishdefault&_m=knowledgebase&_a=viewarticle&parentcategoryid=1&kbarticleid=1063]
+
+
Comparison between the two: [http://support.elgato.com/index.php?languageid=1&group=englishdefault&_m=knowledgebase&_a=viewarticle&parentcategoryid=1&kbarticleid=1203|http://support.elgato.com/index.php?languageid=1&group=englishdefault&_m=knowledgebase&_a=viewarticle&parentcategoryid=1&kbarticleid=1203]
Someone wrote a nice article on how to do it here:
[http://www.bukisa.com/articles/92229_how-to-take-xbox360-screenshots-or-playstation-wii|http://www.bukisa.com/articles/92229_how-to-take-xbox360-screenshots-or-playstation-wii]
They even use a Mac, so the instructions will work for you.