You are not able to create a harmony trigger in IFTTT. There are several WEMO triggers that can end or start a harmony activity but not the other way around.
In my mind IFTTT needs to be treated as a gateway because right now if I add the harmony hub, it shows direct compatibility with WEMO which unfortunately is not the case.
One way compatibility may be a future enhancement to the site as well for cases such as this.
Thanks for the quick reply and love what you have started here, it has great potential!