I just wanted to set the time on my pebble, but there's no more app on the play store. So, after some fun searching, reading, learning, trial, and error...

set-pebble-time.py

import sys
import time
from libpebble2.communication import PebbleConnection
from libpebble2.communication.transports.serial import SerialTransport
from libpebble2.protocol.base import PebblePacket
from libpebble2.protocol.base.types import *
from libpebble2.protocol.system import *

pebble = PebbleConnection(SerialTransport(sys.argv[1])) # argument like /dev/cu.Pebble...
pebble.connect()
pebble.send_packet(TimeMessage(message=SetUTC(utc_offset=-420, tz_name=u"America/Los_Angeles", unix_time=round(time.time()))))