diff --git a/src/buffer/controller.rs b/src/buffer/controller.rs
index 9fd883f..057bda6 100644
--- a/src/buffer/controller.rs
+++ b/src/buffer/controller.rs
@@ -12,7 +12,7 @@ use crate::api::Controller;
 
 use crate::api::TextChange;
 
-use super::tools::InternallyMutable;
+use crate::ext::InternallyMutable;
 
 /// the buffer controller implementation
 ///
diff --git a/src/buffer/mod.rs b/src/buffer/mod.rs
index dfaff9f..1610400 100644
--- a/src/buffer/mod.rs
+++ b/src/buffer/mod.rs
@@ -9,9 +9,6 @@
 /// buffer controller implementation
 pub mod controller;
 
-/// assorted helpers to handle buffer controllers
-pub mod tools;
-
 pub(crate) mod worker;
 
 pub use controller::BufferController as Controller;
diff --git a/src/buffer/tools.rs b/src/ext.rs
similarity index 90%
rename from src/buffer/tools.rs
rename to src/ext.rs
index 0e40359..2bfc362 100644
--- a/src/buffer/tools.rs
+++ b/src/ext.rs
@@ -81,3 +81,11 @@ impl<T: Clone> InternallyMutable<T> {
 		self.getter.borrow().clone()
 	}
 }
+
+pub(crate) struct CallbackHandleWatch<T>(pub(crate) tokio::sync::watch::Sender<Option<T>>);
+
+impl<T> crate::api::controller::CallbackHandle for CallbackHandleWatch<T> {
+	fn unregister(self) {
+		self.0.send_replace(None);
+	}
+}
diff --git a/src/lib.rs b/src/lib.rs
index c2f502f..99390df 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -140,6 +140,9 @@ pub mod prelude;
 /// language-specific ffi "glue"
 pub mod ffi;
 
+/// common utils used in this library and re-exposed
+pub mod ext;
+
 /// underlying OperationalTransform library used, re-exported
 pub use woot;