Hello demonstrates a fairly complete Pebble watch app appMessage implementation including error handling. It outputs a vareity of statistics, and provides convenient settings switches to control some of the app parameters and settings.
The basic appMessage demo apps provided by Pebble demonstrate the key features of the App Message system, but don't illustrate all of the potential errors, warning, and errata that you might encounter on a production app trying to send high rates of data to the Pebble Watch via App Message. The Hello watch app demo attempts to provide a more thorough example. Complete details of the iOS and Watch app implementation can be found in the NOTES.md file.
There is probably some silly bug in here somewhere. If you find something, let me know about it. Thanks!