As far as I can tell, there is exactly one product on the market that is compatible with the my lights: Switchmate. It completely avoids the problem of replacing lights, switches, or indeed anything at all by just physically actuating the existing light switch. It is, by far, the easiest thing to install:

Unfortunately, beyond being compatible with my lights, it solves none of my problems. It isn’t compatible with Alexa, and it isn’t compatible with HomeKit. It promises voice control, but what that really means is that you can tap a microphone button in the app and then speak to your phone. This isn’t really very useful. In fact, as advertised, this product is pretty useless — though it’d be pretty neat if it was the only approximation home automation I had. What it does offer by virtue of having a mobile app, though, was opportunity. They communicate with their mobile apps via Bluetooth LE, and we can emulate that and thereby control them. Conveniently, people have already done this.

So I ordered the parts I would need and set out to make it work:

Three Switchmate BLE switches (two of them the slim/”bright” versions, because the older ones won’t fit side by side on two-gang switches)

One Raspberry Pi 3 model B+ — though I’m pretty sure the Pi Zero W would’ve worked as well, it didn’t have same-day shipping, and I am impatient.

A micro-SD card to put in the Pi

And… that was it. Total cost around $140, but it could’ve been closer to $100 if I were more patient.

Once I received them, I upgraded their firmware to the latest version using the mobile app, snapped them over the relevant switches, and got to making the promised integration happen.

On the software side, I installed the latest Raspbian on the Raspberry Pi, then grabbed a handy Python switchmate tool someone had written (which as far as I can tell is the only up-to-date implementation) to see if it would talk to my switches — and it did! I could experience the joy of turning my kitchen lights on and off from the command line.

Excellent! So now I’m exactly where I was with the phone app, except everything is slightly more inconvenient. But I have my proof of concept, and I can get to work on integration.

For this, I turned to a wonderful project called Homebridge, which lets you add arbitrary devices to Apple’s HomeKit and basically do whatever you like in response to whatever devices you choose to present. There are actually multiple homebridge-switchmate type plugins… but they’re all outdated and won’t necessarily do anything on recent hardware. I instead used homebridge-cmdswitch2 to expose command invocations as HomeKit switches. I simply had it invoke the previous python switchmate tool with the appropriate arguments whenever I needed to throw the switch. This was fine, except that I it needed root permissions. Being lazy, and in flagrant violation of anything ever resembling good practice, I just ran homebridge as root, and everything was good.

This worked! Sometimes. Except when it didn’t. And then it would just stop working entirely no matter how much you tried. In the end, I ended up writing a (terrible, terrible) script that retried several times, and reset the bluetooth stack before each attempt. Apparently the Pi’s integrated BLE does not play nice. For those interested, the script I wrote is over here.

With these retries, the HomeKit integration became reliable, and so I could proceed to the final task: Alexa integration. Conveniently, this has also already been solved by a plugin called homebridge-alexa, which publishes your Homebridge devices for Alexa’s consumption. After setting that up, it worked!