Geek-tools is a set of mobile phone applications for the geek.
Prime number checker: Can check a 64-bit integer for primality.
Al bhed translator: Al bhed is a language spoken by a race in the game Final Fantasy 10. This tool allows you to convert from Al bhed to English and vice versa. The code that does this is very generic so it could be done to any other language and I am open to suggestions. Eg, Elvish.
Binary / Hex / Octal / Decimal / ASCII convertor: So far this is the ‘killer app’ of the tool set. I havnt seen any other J2ME apps with this capability so it may be the first! It can convert between any of the formats to any other format or base.