diff --git a/BizHawk.Emulation/Consoles/Atari/2600/Atari2600.Core.cs b/BizHawk.Emulation/Consoles/Atari/2600/Atari2600.Core.cs
index ece738fc13..ee0b4567e7 100644
--- a/BizHawk.Emulation/Consoles/Atari/2600/Atari2600.Core.cs
+++ b/BizHawk.Emulation/Consoles/Atari/2600/Atari2600.Core.cs
@@ -183,6 +183,7 @@ namespace BizHawk
 
 		public byte ReadControls1()
 		{
+			if (CoreInputComm.InputCallback != null) CoreInputComm.InputCallback();
 			byte value = 0xFF;
 
 			if (Controller["P1 Up"]) value &= 0xEF;
@@ -196,6 +197,7 @@ namespace BizHawk
 
 		public byte ReadControls2()
 		{
+			if (CoreInputComm.InputCallback != null) CoreInputComm.InputCallback();
 			byte value = 0xFF;
 
 			if (Controller["P2 Up"]) value &= 0xEF;
diff --git a/BizHawk.Emulation/Consoles/Calculator/TI83.cs b/BizHawk.Emulation/Consoles/Calculator/TI83.cs
index 4b75c8a1b1..fa287f7af6 100644
--- a/BizHawk.Emulation/Consoles/Calculator/TI83.cs
+++ b/BizHawk.Emulation/Consoles/Calculator/TI83.cs
@@ -126,6 +126,7 @@ namespace BizHawk.Emulation.Consoles.Calculator
 
 		byte ReadKeyboard()
 		{
+			if (CoreInputComm.InputCallback != null) CoreInputComm.InputCallback();
 			//ref TI-9X
 
 			int ret = 0xFF;
diff --git a/BizHawk.Emulation/Consoles/Coleco/ColecoVision.Core.cs b/BizHawk.Emulation/Consoles/Coleco/ColecoVision.Core.cs
index 33085a31bf..a433805826 100644
--- a/BizHawk.Emulation/Consoles/Coleco/ColecoVision.Core.cs
+++ b/BizHawk.Emulation/Consoles/Coleco/ColecoVision.Core.cs
@@ -72,6 +72,7 @@ namespace BizHawk.Emulation.Consoles.Coleco
 
 		public byte ReadControls()
 		{
+			if (CoreInputComm.InputCallback != null) CoreInputComm.InputCallback();
 			byte value = 0xFF;
 
 			if (Controller["P1 Up"]) value &= 0xFF; //TODO;
diff --git a/BizHawk.Emulation/Consoles/Nintendo/Gameboy/Gambatte.cs b/BizHawk.Emulation/Consoles/Nintendo/Gameboy/Gambatte.cs
index b07fad894a..45b3759dfc 100644
--- a/BizHawk.Emulation/Consoles/Nintendo/Gameboy/Gambatte.cs
+++ b/BizHawk.Emulation/Consoles/Nintendo/Gameboy/Gambatte.cs
@@ -86,9 +86,9 @@ namespace BizHawk.Emulation.Consoles.GB
 
 		public IController Controller { get; set; }
 
-		// can when this is called (or not called) be used to give information about lagged frames?
 		LibGambatte.Buttons ControllerCallback()
 		{
+			if (CoreInputComm.InputCallback != null) CoreInputComm.InputCallback();
 			IsLagFrame = false;
 			return CurrentButtons;
 		}
diff --git a/BizHawk.Emulation/Consoles/Nintendo/NES/Core.cs b/BizHawk.Emulation/Consoles/Nintendo/NES/Core.cs
index 58fa7b1620..783e185b03 100644
--- a/BizHawk.Emulation/Consoles/Nintendo/NES/Core.cs
+++ b/BizHawk.Emulation/Consoles/Nintendo/NES/Core.cs
@@ -251,6 +251,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 
 		byte read_joyport(int addr)
 		{
+			if (CoreInputComm.InputCallback != null) CoreInputComm.InputCallback();
 			//read joystick port
 			//many todos here
 			lagged = false;
diff --git a/BizHawk.Emulation/Consoles/Nintendo/SNES/LibsnesCore.cs b/BizHawk.Emulation/Consoles/Nintendo/SNES/LibsnesCore.cs
index 3e893e4bd1..6c84fc197c 100644
--- a/BizHawk.Emulation/Consoles/Nintendo/SNES/LibsnesCore.cs
+++ b/BizHawk.Emulation/Consoles/Nintendo/SNES/LibsnesCore.cs
@@ -453,6 +453,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo.SNES
 
 		ushort snes_input_state(int port, int device, int index, int id)
 		{
+			if (CoreInputComm.InputCallback != null) CoreInputComm.InputCallback();
 			//Console.WriteLine("{0} {1} {2} {3}", port, device, index, id);
 
 			string key = "P" + (1 + port) + " ";
@@ -483,8 +484,8 @@ namespace BizHawk.Emulation.Consoles.Nintendo.SNES
 
 		void snes_input_poll()
 		{
-			// libsnes.cpp calls this on every video refresh regardless of any underlying anything, so...
-			//IsLagFrame = false;
+			// this doesn't actually correspond to anything in the underlying bsnes;
+			// it gets called once per frame with video_refresh() and has nothing to do with anything
 		}
 
 		void snes_input_notify(int index)
diff --git a/BizHawk.Emulation/Consoles/PC Engine/Input.cs b/BizHawk.Emulation/Consoles/PC Engine/Input.cs
index 4e95c242ff..a2dca4aa77 100644
--- a/BizHawk.Emulation/Consoles/PC Engine/Input.cs	
+++ b/BizHawk.Emulation/Consoles/PC Engine/Input.cs	
@@ -39,6 +39,7 @@
 
 		byte ReadInput()
 		{
+			if (CoreInputComm.InputCallback != null) CoreInputComm.InputCallback();
 			byte value = 0x3F;
 
 			int player = SelectedController + 1;
diff --git a/BizHawk.Emulation/Consoles/Sega/Genesis/IO.cs b/BizHawk.Emulation/Consoles/Sega/Genesis/IO.cs
index df5d1980f3..c63421bfdb 100644
--- a/BizHawk.Emulation/Consoles/Sega/Genesis/IO.cs
+++ b/BizHawk.Emulation/Consoles/Sega/Genesis/IO.cs
@@ -106,7 +106,8 @@
 
         void ReadController(ref byte data)
         {
-            data &= 0xC0;
+			if (CoreInputComm.InputCallback != null) CoreInputComm.InputCallback();
+			data &= 0xC0;
             if ((data & 0x40) != 0) // TH high
             {
                 if (Controller["P1 Up"]    == false) data |= 0x01;
diff --git a/BizHawk.Emulation/Consoles/Sega/SMS/Input.cs b/BizHawk.Emulation/Consoles/Sega/SMS/Input.cs
index 71044d8f49..7fc6bf56db 100644
--- a/BizHawk.Emulation/Consoles/Sega/SMS/Input.cs
+++ b/BizHawk.Emulation/Consoles/Sega/SMS/Input.cs
@@ -18,6 +18,7 @@
 
 		byte ReadControls1()
 		{
+			if (CoreInputComm.InputCallback != null) CoreInputComm.InputCallback();
 			lagged = false;
 			byte value = 0xFF;
 
@@ -36,6 +37,7 @@
 
 		byte ReadControls2()
 		{
+			if (CoreInputComm.InputCallback != null) CoreInputComm.InputCallback();
 			lagged = false;
 			byte value = 0xFF;
 
diff --git a/BizHawk.Emulation/Interfaces/CoreComms.cs b/BizHawk.Emulation/Interfaces/CoreComms.cs
index 3973bb6cbe..8a130dfb69 100644
--- a/BizHawk.Emulation/Interfaces/CoreComms.cs
+++ b/BizHawk.Emulation/Interfaces/CoreComms.cs
@@ -20,6 +20,11 @@ namespace BizHawk
 		/// if this is set, then the cpu should dump trace info to CpuTraceStream
 		/// </summary>
 		public TraceBuffer Tracer = new TraceBuffer();
+
+		/// <summary>
+		/// for emu.on_snoop()
+		/// </summary>
+		public System.Action InputCallback;
 	}
 
 	public class CoreOutputComm
diff --git a/BizHawk.MultiClient/LuaImplementation.cs b/BizHawk.MultiClient/LuaImplementation.cs
index b06eed399d..c05572db65 100644
--- a/BizHawk.MultiClient/LuaImplementation.cs
+++ b/BizHawk.MultiClient/LuaImplementation.cs
@@ -378,6 +378,7 @@ namespace BizHawk.MultiClient
 		                                      		"enablerewind",
 													"registerbefore",
 													"registerafter",
+													"on_snoop",
 		                                      	};
 
 		public static string[] MemoryFunctions = new string[]
@@ -1171,6 +1172,27 @@ namespace BizHawk.MultiClient
 			frame_registerafterfunc = luaf;
 		}
 
+		public void emu_on_snoop(LuaFunction luaf)
+		{
+			if (luaf != null)
+			{
+				Global.Emulator.CoreInputComm.InputCallback = delegate()
+				{
+					try
+					{
+						luaf.Call();
+					}
+					catch (SystemException e)
+					{
+						Global.MainForm.LuaConsole1.WriteToOutputWindow(
+							"error running function attached by lua function emu.on_snoop" +
+							"\nError message: " + e.Message);
+					}
+				};
+			}
+
+		}
+
 		//----------------------------------------------------
 		//Memory library
 		//----------------------------------------------------