Worried on losing all your Nike+ data now you have a bigger iPod/Phone to carry?
Marware offer the sporty carry case for both:

The Sportsuit Convertible for iPhone and iPod touch features:

* A 3-in-1 case solution that “converts” to an armband case, a clip-on case, or a slim-profile sleeve
* A clear vinyl cover that protects while providing full usability of the iPhone and iPod touch screen
* Ultra-soft neoprene armband delivers ultimate comfort while the stretchable Velcro® band provides an easily adjustable fit
* A removable armband carrying pouch that conveniently stores cash or keys
* A low-profile belt clip
* The patented Multidapt® clip system allows the iPod or iPhone to be taken in the car, on a bike, to the gym, as well as offering other carrying options (accessories sold separately).