I moved into a new house last year, and I vowed to smart home the crap out of it. That didn't work as intended, because on top of the cost of a new house, I also have the cost of twins. This year, however, is a slightly different story, as I had the spare cash and the opportunity to pick up a few smart home items to get going.
A lot of outdoor timers are really terrible—including most of the ones for the holiday. The dusk-until-dawn timers often don't work, and those that do depend mostly on what the weather outside or the placement of the device is like. For ones that are time-based, the lack of a digital read-out on the lower end ones make it difficult to easily time and set-up.
Alexa doesn't have an outdoor plug. SmartThings doesn't have anything comparable either. There are, however, several 3rd-party devices that will work with Alexa, Google Home, etc. These devices usually work through a 3rd-party skill or compatible application.
In my research, I ended up going with the VAVOFO Outdoor Smart Plug. This is an outdoor quality extension that has 2 or 3 plugs (depending on which device you purchase), and it plugs directly into your outdoor outlets. I've purchased several 3rd-party "smart" devices over the past year, including a nightlight and a desk powerstrip. What I noticed is that they all come in a non-descript yellow box with generic directions, and seem to all be powered by the SmartLife phone application.
I won't lie. I get a little nervous with items such as these, as I'm not sure of the quality control beyond the Amazon reviews, but as long as nothing sounds loose, and the craftmanship seems solid, I'm willing to give it a try.
On the positive side, the VAVOFO is solidly built. The small cord for use when plugging it into your outdoor receptable is sturdy, but can be a bit inflexible when you need to bend the cable. Each plug on the device is equipped with a rubber cover to conceal the plugs you aren't using and protect it from the weather.
Setting up in the SmartLife application is pretty self-explanatory, and the device comes with directions. The auto scan feature of the application doesn't always work, but you can manually add the device if you can track down what you need to add by the icons. These were plugs and it was pretty easy to pick a Wi-Fi socket.
Although these are outdoor plugs, in order to set them up you're best bet is to plug them in inside as close to your Wi-Fi as possible. Have your app ready first. When you go to add a device manually, it'll give you instructions. Sit on the instructions page, plug in the device, and then hold the reset button on the device until it's starts blinking rapidly. Once it is, you can continue with the instructions in the application, which will consist of waiting for the device to be recognized in the application, and then ensuring it has the correct Wi-Fi and Wi-Fi password.
The reason to start in the application is because if you plug it in right away and then move onto the application, the blinking light might stop by the time you're ready, and you'll have to reset the device again.
Once SmartLife has your device installed, if you've connected the application with your Alexa account, Alexa should recognize it immediately, and it'll show up in your list of devices.
A few negatives:
When Alexa picks up the device, it'll pick it up with a generic name like "Plug 1" or something—regardless of if you've renamed it in SmartLife. If you rename it in Alexa, you might come back later and see both the generic device name and the renamed device in Alexa. You can delete the generic one, but Alexa might "rediscover" it later—duplicating your devices. This can be annoying, as it clogs up your device list.
Alexa knows what the devices are by virtue of how the device broadcasts itself. I have a 3-plug and a 2-plug VAVOFO, and one broadcasts itself as plugs, while the other broadcasts itself as switches. This makes them different device types in Alexa, and there is currently no way to correct that.
The great thing about these devices is that you can control the power for each individual plug. This means that with the 2-plug and 3-plug devices, I have 5 individual outdoor plugs I can control with different routines. This worked incredibly well for the Christmas holiday, as I was able to set routines for different sets of lights and other decorations. Ultimately, though, usage of outdoor smart plugs is likely limited to holiday decorations or outdoor landscape lighting, so your mileage may vary as far as return on investment.