umop-apisdn
I finally got around to putting something interactive on
umop-apisdn.org. It takes whatever text you enter and tries to turn it upside down. It works best with lower case text.
I used the Unicode
IPA character set which contains nearly all the upside-down characters I needed. You may find that your browser may or may not render any or all of the IPA characters, so I've provided an ASCII rendering option for backwards compatibility.
¡unɟ əʌɐH