> There are Iridium-based two-way messengers on the market without an externally visible antenna.

I currently own a couple and have owned a bunch of other devices in this category. Have you ever looked at a tear down of one of those devices? Now compare that to a tear down of an iphone? Even supposing Apple can design a much smaller antenna, where is it going to fit? What’s the battery life going to be when it has to send messages periodically (until confirmed) at MUCH higher output power?