I think you'd be better off with a standalone audio recorder. if you're going to be shooting with your iphone, then the mic will only record what is near the iphone, not necessarily what you want to record. if you get a standalone recorder like a zoom h1n you can put the recorder someplace much closer to the actor. also you could get a cheap lav and put it on your actor and connect it to their phone and have them record their dialog in their pocket while shooting.

I'm not aware of any Bluetooth Boom Mics but if there were I would stay away from them as Bluetooth can disconnect and can be unreliable. I always use a Zoom H1n and record the sound separately (it's their cheapest model). I clap in front of the camera so I can sync the audio in post, this way I can get high quality stereo sound with my videos and if anything goes wrong, although it never has so far, I can use the audio from the phone as a last resort.

That rig is just a plastic frame and you can still attach anything to it you like but look for metal ones as the plastic ones flex, most of those reviews are probably fake as people are given these products to test are required to give photos with their reviews. So if you see a product where lots of reviews have photos with them be cautious about buying them.