diff --git a/addons/godot_state_charts/state.gd b/addons/godot_state_charts/state.gd
index 228d3ef..93cc81f 100644
--- a/addons/godot_state_charts/state.gd
+++ b/addons/godot_state_charts/state.gd
@@ -84,7 +84,7 @@ func _process(delta: float) -> void:
 		return
 	
 	# emit processing signal
-	emit_signal("state_processing")
+	emit_signal("state_processing", delta)
 	
 	# process transitions if mode is IDLE
 	if transition_process_mode == ProcessMode.IDLE:
@@ -95,7 +95,7 @@ func _physics_process(delta: float) -> void:
 		return
 	
 	# emit physics processing signal
-	emit_signal("state_processing")
+	emit_signal("state_physics_processing", delta)
 	
 	# process transitions if mode is PHYSICS
 	if transition_process_mode == ProcessMode.PHYSICS:
diff --git a/addons/godot_state_charts/state_chart.gd b/addons/godot_state_charts/state_chart.gd
index dbb6716..3baaa82 100644
--- a/addons/godot_state_charts/state_chart.gd
+++ b/addons/godot_state_charts/state_chart.gd
@@ -2,11 +2,15 @@ tool
 class_name StateChart, "state_chart.svg"
 extends Node
 
+## whether chart should propagate processing events every frame
+export var idle_frame_event: bool = false
+export var physics_frame_event: bool = false
+
 # root state of the state chart
 var _state: State = null
 
 # values available to expression guards
-var _expression_properties: Dictionary = {}
+var _guard_properties: Dictionary = {}
 
 func _ready() -> void:
 	if Engine.editor_hint:
@@ -39,13 +43,22 @@ func send_event(event: String) -> void:
 	_state._state_event(event)
 
 ## sets a property available to guard expressions in transitions
-func set_expression_property(property: String, value) -> void:
-	_expression_properties[property] = value
+func set_guard_property(property: String, value) -> void:
+	_guard_properties[property] = value
 
 func _get_configuration_warning() -> String:
 	if get_child_count() != 1:
 		return "StateChart must have exactly one child"
-	elif not get_child(0) is State:
+	if not get_child(0) is State:
 		return "StateChart's child must be a State"
-	else:
-		return ""
+	return ""
+
+# send frame events that transition can listen to if it should evaluate
+# its guard every frame
+func _process(delta: float) -> void:
+	if idle_frame_event:
+		send_event("idle_frame")
+
+func _physics_process(delta: float) -> void:
+	if physics_frame_event:
+		send_event("physics_frame")
diff --git a/addons/godot_state_charts/transition.gd b/addons/godot_state_charts/transition.gd
index 715104e..0329da8 100644
--- a/addons/godot_state_charts/transition.gd
+++ b/addons/godot_state_charts/transition.gd
@@ -56,7 +56,7 @@ func evaluate_guard() -> bool:
 		return false
 	
 	# combine monitored states with expression properties
-	var properties: Dictionary = root._expression_properties.duplicate()
+	var properties: Dictionary = root._guard_properties.duplicate()
 	for node in checked_states:
 		var state = get_node_or_null(node)
 		if is_instance_valid(state) and state is _State: