Yeah, Bluetooth alone wouldn’t work too well, with its 3 Mbit/s you’d be either sending an HD feed at like 10fps or 480p at 30 fps.
My best suggestion would be for the lens to create a wifi network as soon as it’s turned on that an iPhone can connect to. Some new wifi chips are pretty fast at that, takes only a few seconds.
And depending on how overengineered you can imagine this thing to be, you can even use both — with Bluetooth LE maintaining connection and giving you access to the viewfinder as soon as possible (at lower fps), and then wifi kicking in several seconds later.
Just as The Onion is gradually becoming an actual news website with how crazy the world has become, programmerhumour seems to no longer need to come up with jokes.
Real life is enough :)