New from recently-acquired Sena Cases are iPhone 5 cases based on offerings we've seen for prior-generation devices. LeatherSkin ($45), Magnetic Holster ($45), and WalletSlim ($45) are all leather cases. Magnetic Holster is exactly what its name implies: a belt holster with embedded magnets in the flap to hold it shut. LeatherSkin and WalletSlim are very similar playthrough-style cases. The former comes with a removable ratcheting metal clip, while…