SoundKey, the Nuki Opener alternative for 2-wire intercoms
SoundKey is right for you if Nuki Opener isn't compatible with your 2-wire intercom, if you're a host and want the door to open according to your reservations without paying for extras, or if you don't want to buy a Nuki Bridge. If your intercom is analogue and compatible, or you already use other Nuki products, the Opener may be enough for you.
Nuki Opener vs SoundKey
| SoundKey | Nuki Opener | |
|---|---|---|
| Price | Planned: free device + €10/month (12-month minimum term) | €129 |
| To open remotely | Nothing else: it has WiFi | Nuki Bridge (€99) |
| Airbnb / Booking reservations | Included (iCal and API) | Smart Hosting, €69/year |
| 2-wire intercoms | Yes, if the door-release button is a physical push button | Many not (Fermax Duox, Comelit Simplebus, Golmar Plus, Uno and G2+) |
| How it connects | 2 wires to the door-release button; presses it with a relay | To the intercom's wiring; mimics its signals |
| Power | Rechargeable lithium battery (USB-C) | 4 AAA batteries |
| Guests | Personal link with dates, days and hours | With the Nuki app |
| Availability | Waitlist | On sale |
Nuki prices and compatibility checked on its official website and forum on 22 October 2026. They may change. Nuki and Nuki Opener are trademarks of their respective owners.
Why doesn't Nuki Opener work with my intercom?
Nuki Opener connects to the door entry system's wiring and mimics its signals: the buzzer and the door release. On an analogue intercom those signals are simple, which is why it usually works well.
A digital 2-wire intercom is different. The whole building shares two cables, carrying the voice, the calls and the command to open with each manufacturer's own protocol. To mimic them, Nuki has to know each protocol. Many it doesn't:
- Fermax Duox: not compatible.
- Comelit Simplebus: Nuki lists it as “not compatible”.
- Golmar Plus, Uno and G2+: not compatible.
Nuki itself admits that some systems will never be compatible. And it has withdrawn compatibility that already existed: TCS in 2022 and Siedle in 2025.
How SoundKey does it
SoundKey doesn't mimic any signal. It listens for the buzzer with a microphone and, if it's authorised at that moment, closes the door-release button's contact with a relay. To the intercom, it's the same as pressing it with your finger.
So the brand and the number of wires don't matter. The only requirement is that the door-release button is a physical push button that goes down when you press it. Touch buttons are in development. It also works with video intercoms that have buttons.
When does it open? Only when you've switched it on from the app, during a booking's arrival window, or when a guest has tapped “I'm about to ring” on their link. The rest of the time the buzzer rings as usual.
What each one costs in the first year
Nuki Opener
- Opener: €129
- Nuki Bridge to open remotely: €99
- Smart Hosting for reservations, if you're a host: €69/year
€228 to open remotely. €297 if you also want to connect your reservations.
From the second year on, hosts pay the €69 for Smart Hosting.
SoundKey (planned price)
- Device included: €0
- Service: €10/month, 12-month minimum term
- Remote opening, guest links and reservations included
- The first year of the GoToCheck.pro Premium plan free (€7.45/month + VAT per property)
SoundKey isn't on sale yet and its price may change.
Questions about Nuki Opener and SoundKey
Does Nuki Opener work with 2-wire intercoms?
With some, yes, and with many, no. Because it mimics the intercom's signals, it needs to know each manufacturer's protocol. Fermax Duox, Comelit Simplebus and Golmar Plus, Uno and G2+ are not compatible. SoundKey works with any 2-wire intercom whose door-release button is a physical push button. See compatibility by brand.
How much does Nuki Opener really cost?
The Opener costs €129. To open when you're away from home you need the Nuki Bridge, at €99. If you're a host and want to link it to Airbnb or your PMS, Smart Hosting costs €69 a year. In total, €297 in the first year.
Can I use SoundKey if I already have a Nuki lock?
Yes, they complement each other. SoundKey opens the building's street door and your Nuki lock opens the flat's front door. That way the guest's arrival is covered from start to finish.
Do I need a power socket or a Bridge for SoundKey?
No. It has a rechargeable lithium battery that charges over USB-C, and its own WiFi to open remotely and receive updates. We're measuring real battery life and will publish the figures once testing is finished.
What happens if the internet goes down during an arrival?
If the arrival window was already active, SoundKey keeps opening when the guest rings until that window ends.
Nuki not compatible with your intercom?
Join the waitlist, tell us which intercom you have and we'll let you know when units are available.