Usability Testing Gestures on Mobile Devices

The assignment this week discussed usability using gestures, as well as finishing creating a mobile usability study.  I found creating a study difficult, mostly because of the technical issues involved testing different devices.  But I think in the future that these issues will decrease until eventually there are many different options for mobile UX that are cross platform.  

The questions about gestures seem more difficult to me.  Particularly in regards to cultural differences in a world wide community.  How do we create gestures that make sense for people of such differing backgrounds?  It's a big question, without easy answers.