In contrast you need to hook into Apple APIs / scripting / sqlite databases on trusted apple hardware in order to automate iMessage.

You imagine "Pebble" as one company and say "how hard can it be to turn this on?" As I said in the original comment, it's not that it's hard, it's that it can only be turned on for everyone and that will create a security issue that WILL have a substantial impact on the ecosystem. I didn't say, but believe it to be true that the alternative -- a vendor security assessment program covering software, hardware, architecture and cloud security is not worth Apple's time or money to do. I don't think they have any business reason to do so.