Actually I was able to reproduce this issue on a Pebble Steel, but not on any other watch. It looks like the ready event is getting called, however, in my code I send an app message back to the C portion of the app. This message is failing to send with error message: "The watch app rejected the update that was pushed."
UPDATE: apparently only my Pebble Steel has an issue with the following line of code:
Changing this to the following fixes the issue: