I don't need that, certainly not at a $350 price point!
I wear a bluetooth earbud headset most of the time. This enables me to work hands free, which is helpful because often I have a client on the other end of the phone as I'm working so it's good to be able to multitask that way. I can also listen to books or podcasts while I' working if the work is boring, tedious, mindless. Anyway, if my phone isn't on my person, and I walk too far away from it, I can hear a tone in the earbud the tells me my headset is going to disconnect from the phone. That way I at least know that my phone isn't where I am.
The iPhone also has a couple features that are helpful to me. There is the "find my iPhone" feature, which allows me to see in what geographical location my phone currently is...a helpful tool and one which I put to use recently when I left my phone at the store. I'd been shopping, so it could have been at several stores. I got on my computer and enabled the feature, and it told me that yeah, I'd left it at the Old navy Store a few miles away. The other feature is being able to send a tone alert to my phone from my computer. So if my phone is lost in the house somewhere, even if It's only on vibrate so I won't hear a ring tone, I can send it a message to sound that alert chime, and then I can track it to wherever it is in the house. I've found it between the couch cushions, in the laundry room, on top of the mantel...I'll just randomly, thoughtlessly set it down somewhere, and then have no clue where I'd last used it. Very helpful features!