What would really be useful would be a free Software Defined Radio (SDR) app for the iPhone or iPod;

Something like this;

http://digitalconfections.com/index.php?option=com_content&view=article&id=46&Itemid=54

But you would need a small SDR front end receiver. Basically Just an RF wideband amplifier, local Oscilator and IF mixer before the IF signal is digitally converted by the audio ADC within the iPhone.

Something like this, but using the iPhone + SDR app instead.

http://www.youtube.com/watch?v=mfdgxZPc2BI