Combining your wallet (or credit cards) with your cellphone, is foolish and personally irresponsible.
I understand the idea of consolidation and easy access. But phone snatching is so prevalent these days, because of how mindless phone droning makes people unaware of their surroundings. You’re basically just including your ID, credit cards, etc into one neat little package.
Spread out your loss and theft surface.
I would advise against that myself. If your partner or your hotel cleaner find a diaper sitting out somewhere they probably wont hesitate to throw it in the bin. Then you find youself digging through a dumpster and ripping open diaper after diaper hoping its the one containing your wallet and nothing else.