diff --git a/.env.example b/.env.example
new file mode 100644
index 0000000..3322622
--- /dev/null
+++ b/.env.example
@@ -0,0 +1,10 @@
+# Sox environment variables
+
+# Port to listen on (default: 4567)
+PORT=4567
+
+# Base URL of your Campfire instance (used by the timer command to post notifications)
+CAMPFIRE_URL=https://your-campfire-instance.example.com
+
+# Token used in the notification POST URL path
+CAMPFIRE_TOKEN=your_token_here
diff --git a/cmd_timer.go b/cmd_timer.go
new file mode 100644
index 0000000..89fbcd0
--- /dev/null
+++ b/cmd_timer.go
@@ -0,0 +1,61 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+)
+
+type TimerPlugin struct{}
+
+func (p TimerPlugin) Name() string { return "timer" }
+
+func (p TimerPlugin) ShortHelp() string { return "set a timer" }
+
+func (p TimerPlugin) DetailedHelp() string {
+	return "Usage: timer <duration>\nSets a timer. When it goes off, posts a message to the room.\nExamples: timer 5m, timer 1h30m, timer 90s"
+}
+
+func (p TimerPlugin) Execute(msg BotMessage, args string) string {
+	d, err := time.ParseDuration(strings.TrimSpace(args))
+	if err != nil || d <= 0 {
+		return "Usage: timer &lt;duration&gt; (e.g. timer 5m, timer 1h30m)"
+	}
+
+	if os.Getenv("CAMPFIRE_URL") == "" || os.Getenv("CAMPFIRE_TOKEN") == "" {
+		return "Cannot set timer: CAMPFIRE_URL and CAMPFIRE_TOKEN must be configured."
+	}
+
+	firesAt := time.Now().Add(d)
+
+	go func() {
+		time.Sleep(d)
+		sendTimerNotification(msg, d)
+	}()
+
+	return fmt.Sprintf("Timer set for %s. Will go off at %s.", d, firesAt.Format("15:04:05"))
+}
+
+func sendTimerNotification(msg BotMessage, d time.Duration) {
+	baseURL := os.Getenv("CAMPFIRE_URL")
+	token := os.Getenv("CAMPFIRE_TOKEN")
+	if baseURL == "" || token == "" {
+		log.Println("timer: CAMPFIRE_URL or CAMPFIRE_TOKEN not set, cannot send notification")
+		return
+	}
+
+	url := fmt.Sprintf("%s/rooms/%d/%s/messages", baseURL, msg.Room.ID, token)
+	body := fmt.Sprintf("%s your %s timer is done!", msg.User.Name, d)
+
+	resp, err := http.Post(url, "text/plain", strings.NewReader(body))
+	if err != nil {
+		log.Printf("timer: failed to send notification: %v", err)
+		return
+	}
+	defer resp.Body.Close()
+	io.Copy(io.Discard, resp.Body)
+}
diff --git a/flake.nix b/flake.nix
index df15ee7..6b20c38 100644
--- a/flake.nix
+++ b/flake.nix
@@ -61,7 +61,7 @@
         in
         {
           default = pkgs.mkShell {
-            buildInputs = with pkgs; [ go gopls gotools go-tools ];
+            buildInputs = with pkgs; [ go gopls gotools go-tools libqalculate ];
           };
         });
 
diff --git a/go.mod b/go.mod
index bf83753..d3db718 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,5 @@
 module sox
 
 go 1.22.0
+
+require github.com/joho/godotenv v1.5.1 // indirect
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..d61b19e
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
+github.com/joho/godotenv v1.5.1/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=
diff --git a/main.go b/main.go
index 3bbe436..450595f 100644
--- a/main.go
+++ b/main.go
@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"net/http"
 	"os"
+
+	"github.com/joho/godotenv"
 )
 
 type BotMessage struct {
@@ -35,9 +37,11 @@ func init() {
 	registerPlugin(HiPlugin{})
 	registerPlugin(TracePlugin{})
 	registerPlugin(HelpPlugin{})
+	registerPlugin(TimerPlugin{})
 }
 
 func main() {
+	godotenv.Load()
 	fmt.Println("Sox started")
 	http.HandleFunc("/", commandHandler)