Test Etekcity WiFi Smart Plug, Voltson Mini Outlet with Energy Monitoring (2-Pack), No Hub Required, ETL Listed, White, Works with Alexa, Google Home and IFTTT
So far have not found an API to allow Homeseer to talk to them directly though you can easier connect them via IFTTT. Note however I found I needed to reconnect IFTTT to Etekcity at least once so far to get things working again even though no errors seemed to be reported anywhere in the chain. So a heartbeat system might be in order.
Update I did find this sample code for control via Python you might find useful for creating a plugin or bridge.
Create Homeseer device
First you will want to create a virtual device in Homeseer. Since this maker supports state change triggers for off. on, online and offline make it dimmable
and with and status values like this.
Link through IFTTT
Note it might take IFTTT a few minutes to pick up changes so best of create your virtual devices all up front then wait a bit for proceeding.
As with all such IFTTT linkages you will want at least and off and on IFTTT applet for each direction. In this case we will also want a 5th applet to send offline notices back to Homeseer.
First to control the plug when the Homeseer device changes create and applet like this
To go back the other way create on like this
About the time I started writing this the IFTTT Etekcity linkage seems to have quit working. Checking back a week later it is still not working.