How to insert Unicode characters by their hex codes using USB keyboard on ICS?

Is typing hex codes to insert Unicode characters possible when using USB external keyboard on vanilla ICS or Jelly Bean? Any root modifications available to achieve this?

Or, if not possible system-wide, are there any text editing apps that will allow such behavior?

Inserting Unicode characters such as various bullets, subscript and superscript numbers, Greek letters and so on has been very useful while studying. I normally use gedit on a netbook running peppermint distro, because it's very simple and nondistracting while typing my summaries. I've ended up knowing by heart the most used hex codes. I'm planning to replace the netbook by a cheap vanilla ICS tablet (already factory-rooted) and a comfortable, decent USB keyboard, and the described feature would be mostly appreciated.

Thanks in advance!