I use the Google Messages app and I'm aiming for something like this:

1. I add a custom field called Timezone to my contacts and put in GMT+9 or whatever (I have a friend who's moving to Japan)
2. This theoretical app scans for the time zone field for each member of a chat
3. The app draws over Messages, displaying the time for every time zone it finds in the members of the chat

Does something like this exist? I haven't had luck finding anything.