my wallet is in my right pocket at all times. my phone is always in my hand or to the left (and if not possible, immediate right) of me.
I don't need an app to find either... because I know where they are at all times. If I do put them somewhere, I put them on a designated place they always will be. If either strays, I call the cops. So far, no one has ever stolen my phone or wallet (touch wood)