I've put together a simple mobile compatible web app that calculates exposure from a light reading (Light Candles, Lux or EV).   It would be ideal to use with a memorised EV table (ala Sunny 16) or a cheap light meter without built-in exposure calculation.  It does require a browser with JavaScript support (eg. Opera Mini Beta 4, IE Mobile).

It can be found at shift3.net/exp-calc/