diff --git a/wasp/clock.py b/wasp/clock.py
index 54a5a0e..c3b3c3a 100644
--- a/wasp/clock.py
+++ b/wasp/clock.py
@@ -1,5 +1,7 @@
 import fonts.clock as digits
+import watch
 import widgets
+import manager
 
 from draw565 import Draw565
 
@@ -25,20 +27,40 @@ class ClockApp(object):
     """
 
     def __init__(self):
-        self.on_screen = ( -1, -1, -1, -1, -1, -1 )
         self.meter = widgets.BatteryMeter()
 
-    def draw(self, watch):
+    def handle_event(self, event_view):
+        """Process events that the app is subscribed to."""
+        if event_view[0] == manager.EVENT_TICK:
+            self.update()
+        else:
+            # TODO: Raise an unexpected event exception
+            pass
+
+    def foreground(self, manager, effect=None):
+        """Activate the application."""
+        self.on_screen = ( -1, -1, -1, -1, -1, -1 )
+        self.draw(effect)
+        manager.request_tick(1000)
+
+    def tick(self, ticks):
+        self.update()
+
+    def background(self):
+        """De-activate the application (without losing state)."""
+        pass
+
+    def draw(self, effect=None):
         """Redraw the display from scratch."""
         display = watch.display
 
         display.fill(0)
         display.rleblit(digits.clock_colon, pos=(2*48, 80), fg=0xb5b6)
         self.on_screen = ( -1, -1, -1, -1, -1, -1 )
-        self.update(watch)
+        self.update()
         self.meter.draw()
 
-    def update(self, watch):
+    def update(self):
         """Update the display (if needed).
 
         The updates are a lazy as possible and rely on an prior call to
diff --git a/wasp/manager.py b/wasp/manager.py
index 2c9ab8c..879c3f2 100644
--- a/wasp/manager.py
+++ b/wasp/manager.py
@@ -2,21 +2,51 @@ import clock
 import gc
 import machine
 
+EVENT_TICK = 0x100
+EVENT_KEYMASK = 0xff
+
 class Manager(object):
     def __init__(self, watch):
         self.watch = watch
+
+        self.app = None
         self.switch(clock.ClockApp())
         self.sleep_at = watch.rtc.uptime + 90
         self.charging = True
 
     def switch(self, app):
+        if self.app:
+            self.app.background(self)
+
+        # Clear out any configuration from the old application
+        self.tick_period_ms = 0
+        self.tick_expiry = None
+
         self.app = app
-        app.draw(self.watch)
+        app.foreground(self)
+
+    def request_tick(self, period_ms=None):
+        """Request (and subscribe to) a periodic tick event.
+
+        Note: With the current simplistic timer implementation sub-second
+        tick intervals are not possible.
+        """
+        self.tick_period_ms = period_ms
+        self.tick_expiry = self.watch.rtc.get_uptime_ms() + period_ms
 
     def tick(self):
+        rtc = self.watch.rtc
+
         if self.sleep_at:
-            if self.watch.rtc.update():
-                self.app.update(self.watch)
+            if rtc.update() and self.tick_expiry:
+                now = rtc.get_uptime_ms()
+
+                if self.tick_expiry <= now:
+                    ticks = 0
+                    while self.tick_expiry <= now:
+                        self.tick_expiry += self.tick_period_ms
+                        ticks += 1
+                    self.app.tick(ticks)
 
             if self.watch.button.value():
                 self.sleep_at = self.watch.rtc.uptime + 15
@@ -34,7 +64,7 @@ class Manager(object):
             charging = self.watch.battery.charging()
             if self.watch.button.value() or self.charging != charging:
                 self.watch.display.poweron()
-                self.app.update(self.watch)
+                self.app.tick(None)
                 self.watch.backlight.set(2)
 
                 self.sleep_at = self.watch.rtc.uptime + 15