All of you gadgets freaks see a lot of iPod & iPhone accessories in market, A lot of cases and  arm mounted cases are also available. if you frequent the gym and you should have to check new arm mounted cases from Quirky called Fit kit.
quirkyfitkit gg3 300x233 Quirky Fit Kit Wrap your iPhone on your arm

you can hold your iPhone, iPod and other smartphones or portable mp3 in Fit Kit. It also comes with manner pockets, so you can place your other stuff like cards, ID cards, Credit cards, driving licenses and much more. these pockets are zipped and waterproof, so you have no worry to contact with water. you just wrap you iPhone and other handy gadgets to you arm and forget it. the Fir Kit will cost you $25 on preorder.