Shapecatcher – Find Unicode characters by drawing
shapecatcher.com
shapecatcher.com
My Korean handwriting leaves a lot to be desired, especially on the phone, but it did suggest several similar katakana, so I'm surprised by the omission
> Currently, there are 11817 unicode character glyphs in the database. Japanese, Korean and Chinese characters are currently not supported.
Empty set ∅ and therefore ∴ worked for me too.
Wish someone would turn it into an android keyboard, or at least a layout for anysoftkey.