That's going to need a new method adding to Rockpool. I had a chat with ruff about it, and it seemed to be a good idea to expose the same methods as the Pebble app Javascript API to DBus so that native apps can use them. Sorry I haven't got any further with it yet, I know it's been ages.

Edit: His idea was to create a /org/rockpool/api/apps/<uuid>/ path for each app that can be interacted with. I think it was a good one!