I want to run XBMC on an ARM Tablet, using bluetooth keyboard and an external 4TB hard drive to substitute a typical HTPC.
. P.S.: HTPC doesn't exist as a tag... can someone who is not new here create it?
You can attach an external HDD to the (officially supported) nexus 7 and 10 and play videos. XBMC is not yet available for Ubuntu Touch (as far as I know). There is an XBMC for Android though.