I realize this is an old topic but since it comes up in Google searches and there actually is a proper solution, I'll add it here.
You can put an "overline" on top of any character by following it with Unicode character 'COMBINING OVERLINE' (U+0305). The overline will merge with the character. To do this with a whole word, insert the overline after each character in the word.
eg. RESET becomes R̅E̅S̅E̅T̅
This works everywhere you would want it to — unfortunately, the official "Droid Sans" font doesn't render it very well. It's an imperfect but practical solution.
Alternately, Unicode character 'COMBINING MACRON' (U+0304) can also be used. It works in very much the same way but may not combine with multiple characters as well. I also don't think it is as semantically correct.
Hope that helps someone.