Integration with smart phone cases be damned, there's a reason that standard wallet design hasn't changed in at least a century.
It can't really be improved upon.
Sure, I imagine that the credit card slots have been standardized, and clear spots for photo IDs are probably a later addition, and, of course, keeping photos in wallets wasn't really an option until those were affordable, but the basic wallet design is here to stay.
So, I guess we should all probably learn how to make one.
I love this design by Anna of Noodlehead. Like a lot of great boy-oriented crafts on the web, this one's by a hip mom making something for her son, but that's no matter. A cool guy sewing project is a cool guy sewing project.
Her basic design is solid, and can easily be customized, as in her use of grommets.
Basic Boys Wallet [Noodlehead]