diff --git a/app.py b/app.py
new file mode 100644
index 0000000..0986775
--- /dev/null
+++ b/app.py
@@ -0,0 +1,104 @@
+#!/usr/bin/env python3
+
+import asyncio
+import getpass
+import json
+import os
+import sys
+
+import aiofiles
+
+from nio import AsyncClient, LoginResponse
+
+CONFIG_FILE = "credentials.json"
+
+# Check out main() below to see how it's done.
+
+
+def write_details_to_disk(resp: LoginResponse, homeserver) -> None:
+    """Writes the required login details to disk so we can log in later without
+    using a password.
+
+    Arguments:
+        resp {LoginResponse} -- the successful client login response.
+        homeserver -- URL of homeserver, e.g. "https://matrix.example.org"
+    """
+    # open the config file in write-mode
+    with open(CONFIG_FILE, "w") as f:
+        # write the login details to disk
+        json.dump(
+            {
+                "homeserver": homeserver,  # e.g. "https://matrix.example.org"
+                "user_id": resp.user_id,  # e.g. "@user:example.org"
+                "device_id": resp.device_id,  # device ID, 10 uppercase letters
+                "access_token": resp.access_token,  # cryptogr. access token
+            },
+            f,
+        )
+
+
+async def main() -> None:
+    # If there are no previously-saved credentials, we'll use the password
+    if not os.path.exists(CONFIG_FILE):
+        print(
+            "First time use. Did not find credential file. Asking for "
+            "homeserver, user, and password to create credential file."
+        )
+        homeserver = "https://matrix.example.org"
+        homeserver = input(f"Enter your homeserver URL: [{homeserver}] ")
+
+        if not (homeserver.startswith("https://") or homeserver.startswith("http://")):
+            homeserver = "https://" + homeserver
+
+        user_id = "@user:example.org"
+        user_id = input(f"Enter your full user ID: [{user_id}] ")
+
+        device_name = "matrix-nio"
+        device_name = input(f"Choose a name for this device: [{device_name}] ")
+
+        client = AsyncClient(homeserver, user_id)
+        pw = getpass.getpass()
+
+        resp = await client.login(pw, device_name=device_name)
+
+        # check that we logged in successfully
+        if isinstance(resp, LoginResponse):
+            write_details_to_disk(resp, homeserver)
+        else:
+            print(f'homeserver = "{homeserver}"; user = "{user_id}"')
+            print(f"Failed to log in: {resp}")
+            sys.exit(1)
+
+        print(
+            "Logged in using a password. Credentials were stored.",
+            "Try running the script again to login with credentials.",
+        )
+
+    # Otherwise the config file exists, so we'll use the stored credentials
+    else:
+        # open the file in read-only mode
+        async with aiofiles.open(CONFIG_FILE, "r") as f:
+            contents = await f.read()
+        config = json.loads(contents)
+        client = AsyncClient(config["homeserver"])
+
+        client.access_token = config["access_token"]
+        client.user_id = config["user_id"]
+        client.device_id = config["device_id"]
+
+        # Now we can send messages as the user
+        room_id = "!myfavouriteroomid:example.org"
+        room_id = input(f"Enter room id for test message: [{room_id}] ")
+
+        await client.room_send(
+            room_id,
+            message_type="m.room.message",
+            content={"msgtype": "m.text", "body": "Hello world!"},
+        )
+        print("Logged in using stored credentials. Sent a test message.")
+
+    # Either way we're logged in here, too
+    await client.close()
+
+
+asyncio.run(main())