There have been a couple devices on the market that became somewhat popular with the pool/spa crowd for smart control of pool pumps or heaters.  However, these devices were sold by companies that no longer sell or support them.  Along with this, the control apps are not always reliable and do not get updated any longer.  

Here are two of the devices that are out there.  They appear to have the same hardware manufacturer, and the smartphone apps look like they were designed by the same developer.  No idea how long the servers for the smart app will keep the hardware functional. 

Examples of current devices here:

https://www.amazon.com/WiOn-50054-Electrical-Smartphone-Automated/dp/B00ZYLTJ16

and here:

https://www.amazon.com/DEWENWILS-Outdoor-Wireless-Controller-Compatible/dp/B07PP2KNNH

These type of smart boxes are direct replacements for the standard electromechanical timers typical to pool and spa installs.  

Like this:

https://www.amazon.com/Intermatic-T104-208-277-Volt-Mechanical-Switch/dp/B000BQOX88

Would be nice for a company like TP Link to produce a reliable product like this that worked with the existing app and ecosystem.  It's essentially just the brains from a smart outlet closing a relay rated for 40amps at 120-280volts in an outdoor rated enclosure.