diff --git a/Network/Wai/Handler/DevelServer.hs b/Network/Wai/Handler/DevelServer.hs
--- a/Network/Wai/Handler/DevelServer.hs
+++ b/Network/Wai/Handler/DevelServer.hs
@@ -6,6 +6,7 @@
 import Language.Haskell.Interpreter
 import Network.Wai
 
+import qualified Data.ByteString.Lazy.UTF8 as U
 import qualified Data.ByteString.Lazy.Char8 as L8
 import Network
     ( listenOn, accept, sClose, PortID(PortNumber), Socket
@@ -15,21 +16,26 @@
 import qualified Control.Exception as E
 import System.IO (Handle, hClose)
 import Control.Concurrent (forkIO, threadDelay)
-import Control.Monad (forM)
 
 import qualified Control.Concurrent.MVar as M
 import qualified Control.Concurrent.Chan as C
 import System.Directory (getModificationTime)
 import Network.Wai.Handler.SimpleServer (parseRequest, sendResponse)
+import Control.Monad (filterM)
 
+import Control.Arrow ((&&&))
+import System.Directory (doesDirectoryExist,
+                         doesFileExist, getDirectoryContents)
+import Control.Applicative ((<$>))
+
 type FunctionName = String
 
-run :: Port -> ModuleName -> FunctionName -> IO ()
-run port modu func = do
+run :: Port -> ModuleName -> FunctionName -> [FilePath] -> IO ()
+run port modu func dirs = do
     queue <- C.newChan
     mqueue <- M.newMVar queue
     startApp queue $ loadingApp Nothing
-    _ <- forkIO $ fillApp modu func mqueue
+    _ <- forkIO $ fillApp modu func mqueue dirs
     run' port mqueue
 
 startApp :: Queue -> Handler -> IO ()
@@ -41,21 +47,28 @@
         case msession of
             Nothing -> return ()
             Just (req, onRes) -> do
-                res <- app req
-                -- FIXME exceptions?
-                onRes res
+                void $ forkIO $ (E.handle onErr $ app req) >>= onRes
                 go app
+    onErr :: SomeException -> IO Response
+    onErr e = return
+            $ Response status500 [("Content-Type", "text/plain; charset=utf-8")]
+            $ ResponseLBS $ U.fromString
+            $ "Exception thrown while running application\n\n" ++ show e
+    void x = x >> return ()
 
-fillApp :: String -> String -> M.MVar Queue -> IO ()
-fillApp modu func mqueue =
+fillApp :: String -> String -> M.MVar Queue -> [FilePath] -> IO ()
+fillApp modu func mqueue dirs =
     go Nothing []
   where
+    constSE :: x -> SomeException -> x
+    constSE = const
+    getTimes = E.handle (constSE $ return []) . mapM getModificationTime
     go prevError prevFiles = do
         toReload <-
             if null prevFiles
                 then return True
                 else do
-                    times <- mapM (getModificationTime . fst) prevFiles
+                    times <- getTimes $ map fst prevFiles
                     return $ times /= map snd prevFiles
         (newError, newFiles) <-
             if toReload
@@ -72,19 +85,39 @@
                 putStrLn $ "Compile failed: " ++ show err
                 loadingApp' (Just $ toException err) mqueue
                 return (Just $ toException err, [])
-            Right (app, files) -> do
+            Right (app, files') -> E.handle onInitErr $ do
+                files'' <- mapM fileList dirs
+                let files = concat $ files' : files''
                 putStrLn "Interpreting success, new app loaded"
                 E.handle onInitErr $ do
                     swapApp app mqueue
-                    files' <- forM files $ \f -> do
-                        t <- getModificationTime f
-                        return (f, t)
-                    return (Nothing, files')
+                    times <- getTimes files
+                    return (Nothing, zip files times)
     onInitErr e = do
         putStrLn $ "Error initializing application: " ++ show e
         loadingApp' (Just e) mqueue
         return (Just e, [])
 
+fileList :: FilePath -> IO [FilePath]
+fileList top = do
+    ex <- doesDirectoryExist top
+    if ex then fileList' top "" else return []
+
+fileList' :: FilePath -> FilePath -> IO [FilePath]
+fileList' realTop top = do
+    let prefix1 = top ++ "/"
+        prefix2 = realTop ++ prefix1
+    allContents <- filter notHidden <$> getDirectoryContents prefix2
+    let all' = map ((++) prefix1 &&& (++) prefix2) allContents
+    files <- map snd <$> filterM (doesFileExist . snd) all'
+    dirs <- filterM (doesDirectoryExist . snd) all' >>=
+            mapM (fileList' realTop . fst)
+    return $ concat $ files : dirs
+
+notHidden :: FilePath -> Bool
+notHidden ('.':_) = False
+notHidden _ = True
+
 loadingApp' :: Maybe SomeException -> M.MVar Queue -> IO ()
 loadingApp' err mqueue = swapApp (loadingApp err) mqueue
 
@@ -99,9 +132,11 @@
 loadingApp :: Maybe SomeException -> Handler
 loadingApp err f =
     f $ const $ return $ Response status200
-        [ ("Content-Type", "text/plain")
-        , ("Refresh", "1")
-        ] $ ResponseLBS $ L8.pack $ toMessage err
+        ( ("Content-Type", "text/plain")
+        : case err of
+            Nothing -> [("Refresh", "1")]
+            Just _ -> []
+        ) $ ResponseLBS $ L8.pack $ toMessage err
   where
     toMessage Nothing = "Loading code changes, please wait"
     toMessage (Just err') = "Error loading code: " ++ show err'
diff --git a/wai-handler-devel.cabal b/wai-handler-devel.cabal
--- a/wai-handler-devel.cabal
+++ b/wai-handler-devel.cabal
@@ -1,5 +1,5 @@
 Name:                wai-handler-devel
-Version:             0.0.2
+Version:             0.1.0
 Synopsis:            WAI server that automatically reloads code after modification.
 Description:         This handler automatically reloads your source code upon any changes. It works by using the hint package, essentially embedding GHC inside the handler. The handler (both the executable and library) takes three arguments: the port to listen on, the module name containing the application function, and the name of the function.
                      .
@@ -21,13 +21,15 @@
     location:        git://github.com/snoyberg/wai-handler-devel.git
 
 Library
-  Build-Depends:     base >= 3 && < 5,
-                     wai >= 0.2.1 && < 0.3,
-                     wai-extra >= 0.2.3 && < 0.3,
-                     directory >= 1.0 && < 1.1,
-                     network >= 2.2 && < 2.3,
-                     bytestring >= 0.9 && < 0.10,
-                     hint >= 0.3.2.3 && < 0.4
+  Build-Depends:     base >= 3 && < 5
+                   , wai >= 0.2.1 && < 0.3
+                   , wai-extra >= 0.2.3 && < 0.3
+                   , directory >= 1.0 && < 1.1
+                   , sendfile >= 0.6 && < 0.8
+                   , network >= 2.2 && < 2.3
+                   , bytestring >= 0.9 && < 0.10
+                   , hint >= 0.3.2.3 && < 0.4
+                   , utf8-string >= 0.3 && < 0.4
   Exposed-modules:   Network.Wai.Handler.DevelServer
   ghc-options:       -Wall
 
diff --git a/wai-handler-devel.hs b/wai-handler-devel.hs
--- a/wai-handler-devel.hs
+++ b/wai-handler-devel.hs
@@ -7,19 +7,23 @@
     { port :: Int
     , moduleName :: String
     , function :: String
+    , yesod :: Bool
     }
     deriving (Show, Data, Typeable)
 
 main :: IO ()
 main = do
-    Devel p m f <- cmdArgs Devel
+    Devel p m f y <- cmdArgs Devel
         { port = 3000 &= argPos 0 &= typ "PORT"
         , moduleName = "" &= argPos 1 &= typ "MODULE"
         , function = "" &= argPos 2 &= typ "FUNCTION"
+        , yesod = False &= help "Monitor typical Yesod folders (hamlet, etc)"
         } &= summary "WAI development web server"
-    forkIO $ run p m f
+    _ <- forkIO $ run p m f $ folders y
     go
   where
+    folders False = []
+    folders True = ["hamlet", "cassius", "julius"]
     go = do
         x <- getLine
         case x of