I used a Speck card case for a couple of years but recently switched to a Lifeproof case and wanted something I could use with it.  This pouch attaches perfectly to the back of the Lifeproof case for the iPhone 5.  It doesn't interfere with any of the Lifeproof holders.

Keep in mind that the pouch itself it a tight fit.  I keep a Metrocard and building ID in mine.