i just got an iphone yesterday and while i have some regrets at losing features my blackberry had and apple has yet to incorporate, the apple app store makes up for everything. i've already installed about 30 of these little programs and utilities from the huge pool available.
although i can't offer a review yet since i'm too busy trying to set things up and get everything ported over from my blackberry account, a company called dsrtech has about a half-dozen apps they claim include binaural beats and entrainment. they are called 'brainfreqz'
http://dsrtech.squarespace.com/brainfreqz/
i purchased the ones labeled 'meditation', 'sleep', and 'relaxation'. the descriptions clearly indicate the frequency ranges used for each app. judging from what i've been reading here on this forum, the dsrtech folks absolutely have all the buzz words working so i have high hopes of successfully using these on the go when i can't pull out my procyon.
[btw, i searched for 'brainfreqz' and 'iphone' before i posted this. no hits]
/s~
