Can an xbox360 be connected to a thunderbolt iMac to be used in target display mode I've attempted to do some research, but I've unable to determine if the imac can be used as a monitor (in target display mode) for my xbox 360.

It seems like the only option is some kind of weird converter like the ones that matrox produce for £150! Are there any alternative solutions for input to Thunderbolt ?
Currently, you can only use a 2010 or 2011 27" iMac with this Adapter.

iMacs build in 2009 and before doesn't support input signals. 


  iMacs build in 2010 or 2011 support input, but you have to convert the
  HDMI signal to MiniDisplayPort.


iMacs with Thunderbolt does support input, too. But there is no adapter yet to convert the signals. Thunderbolt is from Intel and they aren't very open about the drivers yet. 

EDIT: Found a german article about your problem.