how about this for an app...

[antholyhotdamn]

A four track recorder/mixer!!! How awesome would that be? Think about it though we have voice recorder, obviously we have script on the phone to adjust volume (for mixing) and our headphone jacks are input and output (I'm guessing based on the mic on the headphones) so really it doesn't seem like a far fetched idea. I wish I knew how to write the app, but the idea of demoing songs on the go with my iPhone is just awesome. I thought I'd bring the idea to some of the brillant minds on this site hopefully some of you are also musicians and can realize how amazing this app would be... On man, imagine if it had an intergrated guitar tuner! Oh man... Off to day dreaming....

[Imahottguy]

Sounds cool, though would be muy dificil to get done... I'd like to able to have two tracks running and have a DJ turntable set up of sorts that would allow me to do my own DJ-ing. That would be pretty tight.

The idea of a guitar tuner based on a line-in cable would be brilliant. Alternate tunings could be done w/ ease. It wouldn't need much of a UI, just six columns (or whatever)(or seven i suppose) and have as little as 4 (for bass obviously). Then it would tell you which string you are hitting, prior to which you have selected the tuning that you want, and then how far off you are!