My router is on the ground floor at the other end of the house. That is a bold concrete ceiling, a steel door, various walls, etcpp. between Wemoswitch and routers. My phone has 0-1 bars Wi-Fi reception.
And yet the wemo switch connectet quite wonderful and constant with the network. No problems!
The only drawback (hence only 4 stars): The Android app is - well - rather mediocre. But also does what it should. But there is still room for improvement. Toll but IFTTT integration!