kivygtk.kv

#:kivy 1.8.0

<Root>:
    orientation: "vertical"

    Button:
        text: "Start GTK thread" if not app.gtk_started else "Stop GTK thread"
        on_release: app.start_gtk_thread()

main.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from kivy.app import App
from kivy.properties import BooleanProperty
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button
from kivy.clock import mainthread
from gi.repository import Gtk, GObject, Gdk, Gio
from threading import Thread

class MyWindow(Gtk.Window):
	def __init__(self):
		self.stat = Gtk.StatusIcon()
		self.stat.set_from_file('icon.png') #choose your own icon
		self.stat.set_visible(True)
	
class GTKThread(Thread):
	def run(self):
		self.win = MyWindow()
		#self.win.connect("delete-event", Gtk.main_quit)
		self.win.show_all()
		GObject.threads_init()
		Gtk.main()

	def stop(self):
		Gtk.main_quit()

class Root(BoxLayout):
	pass

class KivyGTKApp(App):
	gtk_started = BooleanProperty(False)
	
	def build(self):
		return Root()

	def start_gtk_thread(self, *args):
		if self.gtk_started:
			# Stopping the mainloop doesn't work reliably. Avoid doing it.
			self.gtk.stop()
			self.gtk_started = False
		else:
			self.gtk = GTKThread()

			# Set this if you want GTK to (abruptly) shut down with Kivy
			# daemon = True

			# You can probably start more than one thread, if you keep track
			# of every instance
			self.gtk.start()
			self.gtk_started = True

	# This works without the decorator. However you should always
	# use it if you plan to call a method that does GUI stuff from
	# another thread, as it's not thread-safe to do so.
	# Another way to do it is to use Clock to schedule a call to
	# the method.
	#@mainthread
	def add_button(self, text):
		b = Button(text=text, size_hint_y=None, height="30dp")
		self.root.add_widget(b)

	#@mainthread
	def remove_button(self, index):
		if len(self.root.children) > 1:
			self.root.remove_widget(self.root.children[index])

if __name__ == "__main__":
	KivyGTKApp().run()