From the literature what I have gathered is that you will be able to use it only with a wall outlet (socket) where neutral is also present.
In American wiring system where the switch (on/off) acts only as a "circuit breaker" it won't work without the neutral also being present.. Only a regular on/off switch will work. A bell push type (momentary) will not.
I just configure the 2 pieces I received a couple of days ago. The pairing happened ULTRA fast. Then it updated the firmware from 3.0 to 3.3 OTA in under a couple of minutes. Tested the devices using a simple on/off switch. Between the switch and the eWelink software if functioned like a perfect 2 Way switch.
Another, extremely plus point for me, was the feature of working over wifi WITHOUT having to connect to the Internet. There is an option of turning on the lan mode in settings.
Until some more information is available I will be happy to continue using it with current set of features. BTW it is so small that I might replace ALL my Basic devices with these Mini DIY devices.