I see that you can now get an audio recording level meter for iRivers for $99. It isn't the fanciest piece of equipment, but has anyone here tried one of these?

http://www.soundprofessionals.com/cgi-bin/gold/item/ISI-RLM-1

if you use the HD iriver H100 or H300 series you can get big improvment of recording feaures, incl. levelmeter, on the flow adjustment etc. if installing Rockbox.
check out: http://forums.rockbox.org/index.php?topic=2513.0