itsniper
I've been doing iOS development for wearables for a few years and have found that you can generally make BLE for an iOS app very reliable. But it requires some work in the software to cover up some of the underlying flakiness. Reminds me a lot of building resilient networking code for apps back when cell service was slow and spotty. But if you do a little work to build in command queues, auto-reconnect, etc it can be very solid for the user.
Oh, and it helps a lot to pick a good chip. From my experience, the Nordic NRF5x series is the best. But as has been mentioned elsewhere in this post you still need to have a quality antenna design. I've noticed a huge difference between using a reference design and one that spends some time in a chamber with a good RF engineer.