diff --git a/tools/serve.py b/tools/serve.py
new file mode 100755
index 00000000..7006d596
--- /dev/null
+++ b/tools/serve.py
@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+
+"""
+Serve local build with https for testing.
+
+This is useful, e.g. for Android (WebBluetooth doesn't work without https).
+
+Usage:
+
+    yarn build
+    ./tools/serve.py
+
+Browse to https://localhost:8443 on the local machine or
+https://<name-or-address>:8443 on a remote device.
+
+The browser will complain about the self-signed certificate, but this can be
+bypassed (click "Advanced" in browser).
+"""
+
+from http.server import HTTPServer, SimpleHTTPRequestHandler
+from pathlib import Path
+import os
+import ssl
+
+THIS_DIR = Path(__file__).parent
+TEST_CERT = (THIS_DIR / 'test.pem').absolute()
+BUILD_DIR = (THIS_DIR / '..' / 'build').absolute()
+
+# HTTPServer serves the current directory.
+os.chdir(BUILD_DIR)
+
+httpd = HTTPServer(('', 8443), SimpleHTTPRequestHandler)
+httpd.socket = ssl.wrap_socket(httpd.socket, certfile=TEST_CERT, server_side=True)
+httpd.serve_forever()
diff --git a/tools/test.pem b/tools/test.pem
new file mode 100644
index 00000000..85319120
--- /dev/null
+++ b/tools/test.pem
@@ -0,0 +1,48 @@
+-----BEGIN PRIVATE KEY-----
+MIIEvwIBADANBgkqhkiG9w0BAQEFAASCBKkwggSlAgEAAoIBAQDLpTko58nNd2cE
+q8MaB1Wv4xren/xiNomDwf44QK9jZGzvHqnXCKTQ0KsLxtZt7Ne6PU1WdIA3bf6/
+nVzVUhauP0+DF8t6bTH4GSlvLXKGFW6dkCkTMw8ginh73PkZL+OaQvaMVJd42CW9
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+iHBO3yByMs0fLe6UQ/MAHXFVprxnXJ+P2mMe5s/c0BEcTK1deNy9ngKcUvKGCcfj
+T19xtkS4IHS0csz0fkZ+93tGjTm9eCLAOmyvKRljhOMFZKV4J1w4We3Y2b+xHN9w
+psukl2+JAgMBAAECggEBAKacuEZaVYYQQa3VpZs/EwEDavFnrYLhIeM1rXtymMxV
+1rZQvR4ciVP61WaeOMPY+ar7CrJIQLqY+MrmwZQaREotrC0SI703Z6GXXIoEgeVn
+1Yd98c0ughraj7avVPIhdzK3xKWNdBw/o6j2Za2d5Ggt1oWDath2xQOK0eEr1jWu
+VNfZNMvjyvevbyzuBLlF2970ZbOKAi/nrqtmw8mlhqDK5hy+j0K37hAbxizVDmU6
+vZfGhgmgBqXCla59T4rN3StK6zYVfmZKuGHWQbBxbWuLpFA+m09WKF599rUgZG7e
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+RfqL8LjspzUCgYEAqDfl+IlYBOVoDtkR+Kf4p7zi0IVpqp43rffl18ixDqc7XujD
+dmBFdxnSiDEzvEbsg2W/cNGryLSW98XhC9UB5d0rwzz/ZYdh0Ww8CFxQX8pIIZpU
+i1rIWU10+ajud5ynlIS55IP2mxIi38GrtZ4NXpl9JxsRBZ16hiGneV7msCUCgYEA
+iZAVLGve/uJS+x45svU7QkTqqr2Uj084ddHXXyjNamEUttHxvqSXg7cWE4T06jRE
+KmjUXjCQkxo/wuWh6pCiaM3aWdZOBQE3SkBEkKnTICkJ84cSM8iuM7SxYINGxhD1
+1qgMPVeRGmTkPrj/P5cZjANsiVhSjgZHmC0xWbTVo8ECgYBh6R7N4B/xYH+UgV1U
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+iVsnw8OFCSpU/R9P6crPwDEkdZt9miv1BOdh95AqxpmLEJrfXuVNYur0yur7Yv+E
+AVMgdBof4DtucX+v+sLxuHAppA==
+-----END PRIVATE KEY-----
+-----BEGIN CERTIFICATE-----
+MIIDSzCCAjOgAwIBAgIUM9tef51ph3HVoJqF1h7ch5XmOQowDQYJKoZIhvcNAQEL
+BQAwNTELMAkGA1UEBhMCQVUxEzARBgNVBAgMClNvbWUtU3RhdGUxETAPBgNVBAoM
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+NIYo7xQeoorgcNqnV8pIZMh3IUKnL3i9BFrMlhBIZCb/y0XdmJbvb5P9yU3x+z9C
+w1hPKjyhEIYIGnjTh1Rj5feciQSxcouDVOZSgi2iscGePK5734rAzO3zZzbi4lbs
+R2rK2RVrX/s51njLgCHpwPonfEqy8TrMSJvCtH0OG7wQCNbnFOakfzvChpWI/1bI
+Qlai98tuzS49ekXd/dL6lXZi8z7c9Necj21mMgePKQ==
+-----END CERTIFICATE-----