After testing Griffin’s Slap Case, Ozaki’s iCoat Watch ($25), SwitchEasy’s Ticker ($25), and Minimal’s LunaTik Watch Kit ($70), there’s one clear winner in execution—LunaTik—but no single design that completely makes sense in both pricing and practicality. Confronted with the question of whether to do nothing more than sell stylish cloth or plastic wrist straps with attachment holes for the nano’s rear…