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Portable personal security

Know someone is at your door — before they knock.

PreKnock is a camera-free presence sensor that clips onto the inside of the door you don’t control — hotel rooms, short-term rentals, dorms — and alerts your phone the moment someone approaches or lingers outside.

Join the waitlist See how it works

Working prototype · Patent pending · iOS & Android apps · Built in Vancouver, BC

Render of PreKnock, a compact charcoal device with an illuminated button and two status LEDs, on a dark background.
Production-intent render of the working prototype.

Security is built for places, not people.

When you travel or rent, you can’t install cameras or alarms. Door alarms only go off once the door is touched or opened — too late to feel safe. Cameras record everyone in the hallway and often aren’t welcome.

  • Rooms you don’t control
  • Alarms that react too late
  • Cameras that invade privacy

How it works

Three steps. No installation.

  1. 1

    Clip it on.

    Attach the mount to the inside of the door and clip PreKnock on. No drilling, nothing left behind.

  2. 2

    Pair securely.

    PreKnock blinks a pattern that only someone standing in front of it can confirm — it can’t be paired from the hallway.

  3. 3

    Get warned early.

    mmWave radar senses someone approaching. The app tells passers-by apart from someone who stops at your door, and alerts you.

Render of PreKnock clipped onto the inside of a panelled hotel-room door.Render

Seen from above: your room at the top, the hallway below.

Features

Early warning, without a camera.

Render of PreKnock on a light grey background.Render

  • Senses through the door.

    Millimetre-wave radar detects a person on the other side and estimates distance — before any knock.

  • No camera. No recording.

    No images, no audio. Nothing to leak, nothing that makes neighbours uneasy.

  • Works offline.

    Bluetooth alerts to your phone and LEDs on the device. No account or Wi-Fi needed for core alerts.

  • Smart about hallways.

    Adjustable alert distance and a dwell timer, so people walking past don’t trigger alerts.

  • On in seconds, off in seconds.

    A clip-on door mount stays on the door; the device lifts off and goes in your bag.

  • Private pairing.

    Pairing needs someone physically in front of the device.

Design & specs

Small enough to pack. Clear enough to trust.

Render of the front of PreKnock: the illuminated on/off button and a window with two status LEDs.Render
Render of PreKnock in side profile, 37 mm deep.Render

Dimensions

Front dimension drawing of PreKnock: 90 mm wide and 110 mm tall.
Side dimension drawing of PreKnock: 110 mm wide and 37 mm tall.
Specifications (prototype)
Size110 × 90 × 37 mm
Weight~170 g
SensingmmWave radar · ~0.2–7 m range · ~±20 cm distance*
AlertsBluetooth to iOS/Android app · 2 status LEDs
ControlsIlluminated metal on/off button
PowerUSB-C power (runs continuously) or rechargeable lithium battery · ~24 h prototype*, 48 h production target
ConnectivityBluetooth · Wi-Fi (cloud features in development)
MountingClip-on door mount, no tools
PrivacyNo camera · no audio recording

*Measured by the founder on the prototype; not yet independently verified. Design may change before production.

Use cases

For every door you don’t control.

  • Solo & business travellers

    Peace of mind in your hotel room.

  • Short-term rental guests

    No cameras, no installation, no landlord approval.

  • Students & shared housing

    A personal alert for a shared hallway.

  • Hotels (B2B)

    A safety amenity for solo guests.

    Talk to us about a pilot

Our privacy promise

PreKnock senses presence, not identity. It has no camera and records no audio. By default, your alerts stay between your device and your phone. Any cloud features will be optional and opt-in.

FAQ

Frequently asked questions

Is PreKnock available to buy?

Not yet. It’s a working prototype. Join the waitlist and we’ll tell you first when it’s ready.

Does it use a camera or microphone to record?

No. It has no camera and records no audio.

What doors does it work with?

It works best with wood and composite doors. How well it works depends on the door, so we’ll be clear about which doors are supported before you order.

Do I need Wi-Fi or an account?

No. Core alerts work over Bluetooth, offline.

Will I need a subscription?

No. PreKnock works fully without Wi-Fi, an account or a subscription. Optional cloud features, such as alerts when you’re away from the room, may be offered later as an opt-in subscription.

Will people walking past set it off?

You set the alert distance and a dwell time, so passers-by are ignored and someone who stops at your door triggers an alert.

Does it damage the door?

No. The clip-on mount uses a peel-off adhesive and can be taken off.

Can it call the police?

No. PreKnock is an awareness tool. It does not prevent crime, identify people or contact emergency services.

I run a hotel — can we pilot it?

Yes. Use the contact form and choose “Hotel / B2B pilot”.

Waitlist

Be first to know.

PreKnock is a camera-free sensor that warns your phone when someone’s at your door — before they knock. Join the waitlist — be first in line for the founders’ price when pre-orders open.

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Contact

Get in touch.

Questions, press, partnerships or a hotel pilot: send us a note.

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About PreKnock

PreKnock was founded in Vancouver by Farid Masoum, a software engineer with 12+ years of backend and product experience, who designed the product and led the development of the prototype hardware, firmware and apps. We’re building PreKnock for everyone who sleeps behind a door they don’t control.