diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Revision history for Churros
 
+## 0.1.6.0 -- 2022-10-16
+
+* Bump base dependency bounds to allow use of GHC 9.x
+* Fix warnings
+
 ## 0.1.5.1 -- 2020-10-20
 
 * Generalising processes to allow for different transport for process group.
diff --git a/churros.cabal b/churros.cabal
--- a/churros.cabal
+++ b/churros.cabal
@@ -1,6 +1,6 @@
 cabal-version:       2.2
 name:                churros
-version:             0.1.5.0
+version:             0.1.6.0
 license-file:        LICENSE
 author:              Lyndon Maydwell
 maintainer:          lyndon@sordina.net
@@ -24,7 +24,7 @@
 common churros-dependencies
   default-language: Haskell2010
   build-depends:
-    base >= 4.10 && < 4.15,
+    base >= 4.10 && < 4.17,
     time,
     async,
     stm,
@@ -42,7 +42,8 @@
     Control.Churro.Transport,
     Control.Churro.Transport.Chan
     Control.Churro.Transport.Unagi
-    Control.Churro.Transport.Unagi.Bounded
+    Control.Churro.Transport.MVar
+    Control.Churro.Transport.MVar.Latest
 
 test-suite churros-test
   import:            churros-dependencies
@@ -59,4 +60,6 @@
     Control.Churro.Transport.Chan
     Control.Churro.Transport.Unagi
     Control.Churro.Transport.Unagi.Bounded
+    Control.Churro.Transport.MVar
+    Control.Churro.Transport.MVar.Latest
     Churro.Test.Examples
diff --git a/src/Control/Churro/Transport/MVar.hs b/src/Control/Churro/Transport/MVar.hs
new file mode 100644
--- /dev/null
+++ b/src/Control/Churro/Transport/MVar.hs
@@ -0,0 +1,34 @@
+{-# LANGUAGE TypeFamilies #-}
+{-# OPTIONS_GHC -Wno-orphans #-}
+{-# LANGUAGE BlockArguments #-}
+
+-- | MVar Transport Instance. Blocks when item hasn't been consumed downstream.
+
+module Control.Churro.Transport.MVar where
+    
+import Control.Churro.Types
+import Control.Churro.Prelude
+
+import Control.Concurrent
+import Data.Void
+
+instance Transport MVar where
+    data In  MVar a = ChanIn  (MVar a)
+    data Out MVar a = ChanOut (MVar a)
+    yank (ChanOut c) = takeMVar c
+    yeet (ChanIn  c) = putMVar  c
+    flex = do 
+        c <- newEmptyMVar
+        return (ChanIn c, ChanOut c)
+
+type ChurroMVar a = Churro a MVar
+
+-- | Convenience function for running a Churro with an MVar Transport.
+-- 
+runWaitMVar :: ChurroMVar a Void Void -> IO a
+runWaitMVar = runWait
+
+-- | Convenience function for running a Churro into a List with an MVar Transport.
+-- 
+runWaitListMVar :: ChurroMVar () Void o -> IO [o]
+runWaitListMVar = runWaitList
diff --git a/src/Control/Churro/Transport/MVar/Latest.hs b/src/Control/Churro/Transport/MVar/Latest.hs
new file mode 100644
--- /dev/null
+++ b/src/Control/Churro/Transport/MVar/Latest.hs
@@ -0,0 +1,43 @@
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# OPTIONS_GHC -Wno-orphans #-}
+{-# LANGUAGE BlockArguments #-}
+
+-- | MVar Transport Instance. New items overwrite the current queued item.
+-- 
+-- Useful in subscription-like contexts where you don't care about outdated values.
+-- 
+-- This is surprisingly useful since it doesn't block sources, but also doesn't accumulate items.
+-- 
+-- WARNING: Don't use if you want to ensure that all produced items are consumed!
+-- 
+module Control.Churro.Transport.MVar.Latest where
+    
+import Control.Churro.Types
+import Control.Churro.Prelude
+
+import Control.Concurrent
+import Data.Void
+
+data Latest a where
+
+instance Transport Latest where
+    data In  Latest a    = ChanIn  (MVar a)
+    data Out Latest a    = ChanOut (MVar a)
+    yank (ChanOut c)   = takeMVar c
+    yeet (ChanIn  c) v = tryTakeMVar c >> putMVar  c v
+    flex = do 
+        c <- newEmptyMVar
+        return (ChanIn c, ChanOut c)
+
+type ChurroLatest a = Churro a Latest
+
+-- | Convenience function for running a Churro with a MVar backed Latest Transport.
+-- 
+runWaitLatest :: ChurroLatest a Void Void -> IO a
+runWaitLatest = runWait
+
+-- | Convenience function for running a Churro into a List with a MVar backed Latest Transport.
+-- 
+runWaitListLatest :: ChurroLatest () Void o -> IO [o]
+runWaitListLatest = runWaitList
diff --git a/src/Control/Churro/Transport/Unagi/Bounded.hs b/src/Control/Churro/Transport/Unagi/Bounded.hs
--- a/src/Control/Churro/Transport/Unagi/Bounded.hs
+++ b/src/Control/Churro/Transport/Unagi/Bounded.hs
@@ -50,13 +50,15 @@
 runWaitListUnagi :: KnownNat n => ChurroUnagiBounded () n Void o -> IO [o]
 runWaitListUnagi = runWaitList
 
--- A version of processes that mandates the use of a single item buffer for the internal processes.
+-- | A version of processes that mandates the use of a single item buffer for the internal processes.
+-- 
 -- This is useful in order to prevent allocating to processes that are not yet idle.
 -- 
 processesUnagi :: (Traversable f, Transport t, Monoid a) => f (ChurroUnagiBounded a 1 i o) -> Churro a t i o
 processesUnagi = processes
 
--- A version of thief that mandates the use of a single item buffer for the internal processes.
+-- | A version of thief that mandates the use of a single item buffer for the internal processes.
+-- 
 -- This is useful in order to prevent allocating to processes that are not yet idle.
 -- 
 thiefUnagi :: (Transport t, Monoid a) => Int -> ChurroUnagiBounded a 1 i o -> Churro a t i o
diff --git a/src/Control/Churro/Types.hs b/src/Control/Churro/Types.hs
--- a/src/Control/Churro/Types.hs
+++ b/src/Control/Churro/Types.hs
@@ -15,6 +15,7 @@
 import Control.Category
 import Control.Concurrent.Async (cancel, wait, Async, async)
 import Data.Void
+import Data.Kind (Type)
 import Control.Exception (finally)
 
 -- $setup
@@ -64,9 +65,9 @@
 -- Channels like Chan that have a single channel act as in/out simply reuse the
 -- same channel in the pair returned.
 -- 
-class Transport (t :: * -> *) where
-    data In  t :: * -> *
-    data Out t :: * -> *
+class Transport (t :: Type -> Type) where
+    data In  t :: Type -> Type
+    data Out t :: Type -> Type
     flex :: IO (In t a, Out t a)  -- ^ Create a new pair of Transports.
     yank :: Out t a -> IO a       -- ^ Yank an item off the Transport
     yeet :: In t a -> a -> IO ()  -- ^ Yeet an item onto the Transport
@@ -143,13 +144,13 @@
                 fx <- yank fo
                 gx <- yank go
                 case (fx, gx) of
-                    (Just f', Just g') -> (yeet o $ Just (f' g')) >> prog
+                    (Just f', Just g') -> yeet o (Just (f' g')) >> prog
                     _                  -> return ()
 
         -- TODO: Should we cancel asyncs here in finally block?
         prog
         yeet o Nothing
-        wait fa
+        _ <- wait fa
         wait ga
 
 -- | More general variant of `pure` with Monoid constraint.
diff --git a/test/Churro/Test/Examples.hs b/test/Churro/Test/Examples.hs
--- a/test/Churro/Test/Examples.hs
+++ b/test/Churro/Test/Examples.hs
@@ -16,7 +16,9 @@
 
 import Control.Churro
 import Control.Concurrent.Async (wait)
-import Control.Concurrent (Chan)
+import Control.Concurrent (MVar, Chan)
+import Control.Churro.Transport.MVar ()
+import Control.Churro.Transport.MVar.Latest (Latest)
 
 -- $setup
 -- 
@@ -63,6 +65,25 @@
     where
     maps    = map fromList $ zipWith zip updates updates
     updates = map (take 2) (tails [0 :: Int ..])
+
+-- | Combination of different transports:
+
+mvarTest :: Churro () MVar Void Void
+mvarTest = sourceIO @MVar (\cb -> cb (1 :: Int) >> cb 2 >> cb 3) >>> delay 1 >>> sinkPrint
+
+latestTest :: Churro () Latest Void Void
+latestTest = sourceIO @Latest (\cb -> cb (1 :: Int) >> cb 2 >> cb 3) >>> delay 1 >>> sinkPrint
+
+-- | Should only output the latest values after sink is free to consume
+-- 
+-- >>> runWait mvarTest
+-- 1
+-- 2
+-- 3
+
+-- >>> runWait latestTest
+-- 1
+-- 3
 
 -- | Consumers terminaiting should kill sources from producing.
 --