Android phones, apps and tablets

^^^Set your language to US english in the voice settings and ok google should work fine (or at least it does with my galaxy nexus). Only works from within the stock launcher though, so you won't be able to use it from inside apps or another launcher.

Switching to US English worked for me, feels kind of dirty to me now though.

Only works when I'm in Google Now though, probably 'cos it is now supported by the launcher. Hopefully the guy who deved it can add that functionally.