alexa-smart-home-virtualbuttons

Alexa Smart Home Virtual Buttons

Background

It's sometimes useful to have Alexa announce things and have these triggered from real world actions (e.g. "Garage door is open", "Washing machine has finished").

If you've used Home Assistant then you might know of an unofficial Alexa plugin. This is a pretty clever piece of work, with a lot of reverse-engineered API discovery. And, yes, it can make these announcements.

However I have a problem with it; because it's all unofficial APIs it sometimes break. And, in my case, weekly it would lock out my Amazon account with multiple authentication failures. If Amazon would just publish an official API then this wouldn't be a problem, but... sigh.

So since I didn't need most of the I wondered if there was another way

The official way

Alexa recently got the ability to trigger routines from Smart Home sensors; specifically Door Sensors and Motion Sensors. If a Door Sensor switched to "open" then a routine can be triggered. And one of the actions can be to announce... anything you want it to say.

So all we need to do is add some "virtual buttons" (masquerading as door sensors) which can be triggered by a HTTPS request and we're done!

Some searching around the 'net found a couple of solutions out there; I haven't tried them but I'm guessing (based on their description) that they work in a similar way.

If you're willing to pay someone else to do the heavy lifting then these are possible solutions:

Sinric: First 3 devices free, $3/device/yr after that.

Virtual Buttons: First device free; 2 devices $12/yr, 5 devices $24/year, 10 devices $36/year.

Note: I'm not endorsing these at all; they're just what I found. They also likely to be 100 times more polished than this (pretty user interfaces). This code is "raw".

If you're willing to put in the effort in setting this up then we can use the code in this repo to create a Smart Home skill that presents as door sensors, and allows you to use them as Alexa routine triggers.

Design

A Smart Home skill has to be hosted in Amazon Lambda, so I decided to make this "Cloud Native". We use a DynamoDB table to hold the button definitions (and some other additional data), the Lambda Function (written in Go) and a HTTP API Gateway to allow for control.

The Lambda hosting and DynamoDB are "always free" within the limits we will be using it. The API Gateway costs $1 for 1,000,000 requests in a month. If we called it once every 5 minutes for a whole month that's under 10,000 requests, which may cost 1c. More realistly this will cost zero. The COSTS provides a detailed analyse.

Installation

Please read the Installation documents

Usage

Please read the Usage