diff --git a/src/reagent/ratom.cljs b/src/reagent/ratom.cljs
index 7539c18..863efc4 100644
--- a/src/reagent/ratom.cljs
+++ b/src/reagent/ratom.cljs
@@ -103,10 +103,40 @@
 
 
 
-;;; cursor
+;;; monitor
 
 (declare make-reaction)
 
+(defonce cached-reactions {})
+
+(defn- cached-reaction [obj key f]
+  (if-some [r (get cached-reactions [key])]
+    r
+    (if (some? *ratom-context*)
+      (let [r (make-reaction
+               f :on-dispose #(set! cached-reactions
+                                    (dissoc cached-reactions key)))
+            v (-deref r)]
+        (set! cached-reactions (assoc cached-reactions key f))
+        (set! (.-reaction obj) r)
+        v)
+      (f))))
+
+(deftype Monitor [f args ^:mutable reaction]
+  IReactiveAtom
+
+  IDeref
+  (-deref [this]
+    (if-some [r reaction]
+      (-deref r)
+      (cached-reaction this [f args]
+                       #(apply f args)))))
+
+(defn monitor [f & args]
+  (Monitor. f args nil))
+
+;;; cursor
+
 (deftype RCursor [ratom path ^:mutable reaction]
   IAtom
   IReactiveAtom
@@ -479,7 +509,7 @@
             (util/partial-ifn. callback-fn args nil)
             false nil))
 
-(do
+(comment
   (def perf-check 0)
   (defn ratom-perf []
     (dbg "ratom-perf")
diff --git a/test/reagenttest/runtests.cljs b/test/reagenttest/runtests.cljs
index 5ae560c..40f0bf3 100644
--- a/test/reagenttest/runtests.cljs
+++ b/test/reagenttest/runtests.cljs
@@ -4,6 +4,7 @@
             [reagenttest.testinterop]
             [reagenttest.testratom]
             [reagenttest.testratomasync]
+            [reagenttest.testmonitor]
             [reagenttest.testwrap]
             [cljs.test :as test :include-macros true]
             [reagent.core :as r]
diff --git a/test/reagenttest/testmonitor.cljs b/test/reagenttest/testmonitor.cljs
new file mode 100644
index 0000000..ee4686e
--- /dev/null
+++ b/test/reagenttest/testmonitor.cljs
@@ -0,0 +1,255 @@
+(ns reagenttest.testmonitor
+  (:require [cljs.test :as t :refer-macros [is deftest testing]]
+            [reagent.ratom :as rv :refer [monitor]
+             :refer-macros [run! reaction]]
+            [reagent.debug :refer-macros [dbg]]
+            [reagent.core :as r]))
+
+(defn running []
+  (set! rv/debug true)
+  (rv/running))
+
+(def testite 10)
+
+(defn dispose [v]
+  (rv/dispose! v))
+
+(enable-console-print!)
+
+
+(deftest basic-ratom
+  (let [runs (running)
+        start (rv/atom 0)
+        svf (fn [] @start)
+        sv (monitor svf)
+        compf (fn [x] @sv (+ x @sv))
+        comp (monitor compf 2)
+        c2f (fn [] (inc @comp))
+        count (rv/atom 0)
+        out (rv/atom 0)
+        resf (fn []
+               (swap! count inc)
+               (+ @sv @(monitor c2f) @comp))
+        res (monitor resf)
+        const (run!
+               (reset! out @res))]
+    (is (= @count 1) "constrain ran")
+    (is (= @out 5))
+    (reset! start 1)
+    (is (= @out 8))
+    (is (= @count 2))
+    (dispose const)
+    (is (= (running) runs))))
+
+(deftest double-dependency
+  (let [runs (running)
+        start (rv/atom 0)
+        c3-count (rv/atom 0)
+        c1 (reaction @start 1)
+        c2 (reaction @start)
+        c3 (rv/make-reaction
+            (fn []
+              (swap! c3-count inc)
+              (+ @c1 @c2))
+            :auto-run true)]
+    (is (= @c3-count 0))
+    (is (= @c3 1))
+    (is (= @c3-count 1) "t1")
+    (swap! start inc)
+    (is (= @c3-count 2) "t2")
+    (is (= @c3 2))
+    (is (= @c3-count 2) "t3")
+    (dispose c3)
+    (is (= (running) runs))))
+
+(deftest test-from-reflex
+  (let [runs (running)]
+    (let [!counter (rv/atom 0)
+          !signal (rv/atom "All I do is change")
+          co (run!
+              ;;when I change...
+              @!signal
+              ;;update the counter
+              (swap! !counter inc))]
+      (is (= 1 @!counter) "Constraint run on init")
+      (reset! !signal "foo")
+      (is (= 2 @!counter)
+          "Counter auto updated")
+      (dispose co))
+    (let [!x (rv/atom 0)
+          !co (rv/make-reaction #(inc @!x) :auto-run true)]
+      (is (= 1 @!co) "CO has correct value on first deref") 
+      (swap! !x inc) 
+      (is (= 2 @!co) "CO auto-updates")
+      (dispose !co))
+    (is (= runs (running)))))
+
+
+(deftest test-unsubscribe
+  (dotimes [x testite]
+    (let [runs (running)
+          a (rv/atom 0)
+          a1 (reaction (inc @a))
+          a2 (reaction @a)
+          b-changed (rv/atom 0)
+          c-changed (rv/atom 0)
+          b (reaction
+             (swap! b-changed inc)
+             (inc @a1))
+          c (reaction
+             (swap! c-changed inc)
+             (+ 10 @a2))
+          res (run!
+               (if (< @a2 1) @b @c))]
+      (is (= @res (+ 2 @a)))
+      (is (= @b-changed 1))
+      (is (= @c-changed 0))
+             
+      (reset! a -1)
+      (is (= @res (+ 2 @a)))
+      (is (= @b-changed 2))
+      (is (= @c-changed 0))
+             
+      (reset! a 2)
+      (is (= @res (+ 10 @a)))
+      (is (<= 2 @b-changed 3))
+      (is (= @c-changed 1))
+             
+      (reset! a 3)
+      (is (= @res (+ 10 @a)))
+      (is (<= 2 @b-changed 3))
+      (is (= @c-changed 2))
+             
+      (reset! a 3)
+      (is (= @res (+ 10 @a)))
+      (is (<= 2 @b-changed 3))
+      (is (= @c-changed 2))
+             
+      (reset! a -1)
+      (is (= @res (+ 2 @a)))
+      (dispose res)
+      (is (= runs (running))))))
+
+(deftest maybe-broken
+  (let [runs (running)]
+    (let [runs (running)
+          a (rv/atom 0)
+          b (reaction (inc @a))
+          c (reaction (dec @a))
+          d (reaction (str @b))
+          res (rv/atom 0)
+          cs (run!
+              (reset! res @d))]
+      (is (= @res "1"))
+      (dispose cs))
+    ;; should be broken according to https://github.com/lynaghk/reflex/issues/1
+    ;; but isnt
+    (let [a (rv/atom 0)
+          b (reaction (inc @a))
+          c (reaction (dec @a))
+          d (run! [@b @c])]
+      (is (= @d [1 -1]))
+      (dispose d))
+    (let [a (rv/atom 0)
+          b (reaction (inc @a))
+          c (reaction (dec @a))
+          d (run! [@b @c])
+          res (rv/atom 0)]
+      (is (= @d [1 -1]))
+      (let [e (run! (reset! res @d))]
+        (is (= @res [1 -1]))
+        (dispose e))
+      (dispose d))
+    (is (= runs (running)))))
+
+(deftest test-dispose
+  (dotimes [x testite]
+    (let [runs (running)
+          a (rv/atom 0)
+          disposed (rv/atom nil)
+          disposed-c (rv/atom nil)
+          disposed-cns (rv/atom nil)
+          count-b (rv/atom 0)
+          b (rv/make-reaction (fn []
+                                (swap! count-b inc)
+                                (inc @a))
+                              :on-dispose #(reset! disposed true))
+          c (rv/make-reaction #(if (< @a 1) (inc @b) (dec @a))
+                              :on-dispose #(reset! disposed-c true))
+          res (rv/atom nil)
+          cns (rv/make-reaction #(reset! res @c)
+                                :auto-run true
+                                :on-dispose #(reset! disposed-cns true))]
+      @cns
+      (is (= @res 2))
+      (is (= (+ 4 runs) (running)))
+      (is (= @count-b 1))
+      (reset! a -1)
+      (is (= @res 1))
+      (is (= @disposed nil))
+      (is (= @count-b 2))
+      (is (= (+ 4 runs) (running)) "still running")
+      (reset! a 2)
+      (is (= @res 1))
+      (is (= @disposed true))
+      (is (= (+ 2 runs) (running)) "less running count")
+
+      (reset! disposed nil)
+      (reset! a -1)
+      ;; This fails sometimes on node. I have no idea why.
+      (is (= 1 @res) "should be one again")
+      (is (= @disposed nil))
+      (reset! a 2)
+      (is (= @res 1))
+      (is (= @disposed true))
+      (dispose cns)
+      (is (= @disposed-c true))
+      (is (= @disposed-cns true))
+      (is (= runs (running))))))
+
+(deftest test-on-set
+  (let [runs (running)
+        a (rv/atom 0)
+        b (rv/make-reaction #(+ 5 @a)
+                            :auto-run true
+                            :on-set (fn [oldv newv]
+                                      (reset! a (+ 10 newv))))]
+    @b
+    (is (= 5 @b))
+    (reset! a 1)
+    (is (= 6 @b))
+    (reset! b 1)
+    (is (= 11 @a))
+    (is (= 16 @b))
+    (dispose b)
+    (is (= runs (running)))))
+
+(deftest non-reactive-deref
+  (let [runs (running)
+        a (rv/atom 0)
+        b (rv/make-reaction #(+ 5 @a))]
+    (is (= @b 5))
+    (is (= runs (running)))
+
+    (reset! a 1)
+    (is (= @b 6))
+    (is (= runs (running)))))
+
+(deftest catching
+  (let [runs (running)
+        a (rv/atom false)
+        catch-count (atom 0)
+        b (reaction (if @a (throw (js/Error. "fail"))))
+        c (run! (try @b (catch :default e
+                          (swap! catch-count inc))))]
+    (set! rv/silent true)
+    (is (= @catch-count 0))
+    (reset! a false)
+    (is (= @catch-count 0))
+    (reset! a true)
+    (is (= @catch-count 1))
+    (reset! a false)
+    (is (= @catch-count 1))
+    (set! rv/silent false)
+    (dispose c)
+    (is (= runs (running)))))