.... who can't remember all the formulas and how to read resistors with 6
bands, and need to know the forward voltages of LEDs and can never remember
the connections to an LM317, or the formula to calculate the resistor
values, or the configuration of an RC tone stack filter and and and ...

RS Toolkit. New app for iPad and iPhone. Free, and very good !

Not sure if it will be on any iTunes Stores outside the UK, but worth a look

Arfa