Four companies have released form-fitting, “play-through” iPhone cases made from reinforced leather. In alphabetical order, BoxWave has the Designio Open Screen Leather Sleeve ($44/$30), Case-Mate is selling the Signature Leather Case ($35), Macally has the mCase ($20), and Pacific Rim Technologies is selling iShield for iPhone ($35). These cases all have a design concept in common—they cover iPhone’s body while exposing…