From Ssu Jen Lu:
Mandarin Helper is an iPhone/iPod Touch application which provides the Chinese character look-up function by requiring only a part of the character, called "radical". It will list all characters from the hsk level 1-4 which contains the particular radical. The user select the character from the search result list, then the program will display words list from the dictionary. The definition part displays the meanings of the word as well as "Pinyin". To search radicals, simplified Chinese character keyboard (OS X Touch builtin) must be used.