diff --git a/relaypool.go b/relaypool.go
index 4c76ecf..2a79c8c 100644
--- a/relaypool.go
+++ b/relaypool.go
@@ -60,33 +60,41 @@ func NewRelayPool() *RelayPool {
 
 // Add adds a new relay to the pool, if policy is nil, it will be a simple
 // read+write policy.
-func (r *RelayPool) Add(url string, policy RelayPoolPolicy) error {
+func (r *RelayPool) Add(url string, policy RelayPoolPolicy) chan error {
 	if policy == nil {
 		policy = SimplePolicy{Read: true, Write: true}
 	}
 
-	relay, err := RelayConnect(url)
-	if err != nil {
-		return err
-	}
+	cherr := make(chan error)
 
-	r.Policies.Store(relay.URL, policy)
-	r.Relays.Store(relay.URL, relay)
+	go func() {
+		relay, err := RelayConnect(url)
+		if err != nil {
+			cherr <- fmt.Errorf("failed to connect to %s: %w", url, err)
+			return
+		}
 
-	r.subscriptions.Range(func(id string, filters Filters) bool {
-		sub := relay.subscribe(id, filters)
-		eventStream, _ := r.eventStreams.Load(id)
+		r.Policies.Store(relay.URL, policy)
+		r.Relays.Store(relay.URL, relay)
 
-		go func(sub *Subscription) {
-			for evt := range sub.Events {
-				eventStream <- EventMessage{Relay: relay.URL, Event: evt}
-			}
-		}(sub)
+		r.subscriptions.Range(func(id string, filters Filters) bool {
+			sub := relay.subscribe(id, filters)
+			eventStream, _ := r.eventStreams.Load(id)
 
-		return true
-	})
+			go func(sub *Subscription) {
+				for evt := range sub.Events {
+					eventStream <- EventMessage{Relay: relay.URL, Event: evt}
+				}
+			}(sub)
 
-	return nil
+			return true
+		})
+
+		cherr <- nil
+		close(cherr)
+	}()
+
+	return cherr
 }
 
 // Remove removes a relay from the pool.
@@ -101,7 +109,7 @@ func (r *RelayPool) Remove(url string) {
 	}
 }
 
-func (r *RelayPool) Sub(filters Filters) (string, chan EventMessage, chan Event) {
+func (r *RelayPool) Sub(filters Filters) (string, chan EventMessage) {
 	random := make([]byte, 7)
 	rand.Read(random)
 	id := hex.EncodeToString(random)
@@ -109,8 +117,6 @@ func (r *RelayPool) Sub(filters Filters) (string, chan EventMessage, chan Event)
 	r.subscriptions.Store(id, filters)
 	eventStream := make(chan EventMessage)
 	r.eventStreams.Store(id, eventStream)
-	uniqueEvents := make(chan Event)
-	emittedAlready := s.MapOf[string, struct{}]{}
 
 	r.Relays.Range(func(_ string, relay *Relay) bool {
 		sub := relay.subscribe(id, filters)
@@ -118,16 +124,28 @@ func (r *RelayPool) Sub(filters Filters) (string, chan EventMessage, chan Event)
 		go func(sub *Subscription) {
 			for evt := range sub.Events {
 				eventStream <- EventMessage{Relay: relay.URL, Event: evt}
-				if _, ok := emittedAlready.LoadOrStore(evt.ID, struct{}{}); !ok {
-					uniqueEvents <- evt
-				}
 			}
 		}(sub)
 
 		return true
 	})
 
-	return id, eventStream, uniqueEvents
+	return id, eventStream
+}
+
+func Unique(all chan EventMessage) chan Event {
+	uniqueEvents := make(chan Event)
+	emittedAlready := s.MapOf[string, struct{}]{}
+
+	go func() {
+		for eventMessage := range all {
+			if _, ok := emittedAlready.LoadOrStore(eventMessage.Event.ID, struct{}{}); !ok {
+				uniqueEvents <- eventMessage.Event
+			}
+		}
+	}()
+
+	return uniqueEvents
 }
 
 func (r *RelayPool) PublishEvent(evt *Event) (*Event, chan PublishStatus, error) {