First off, the Android app for WeMo switches is awful. If you’re an Android person and don’t have an iOS device on hand to set these things up, forget it.
Second, they’ve had their share of security issues, which are hopefully fixed now. The worst-case scenario of these threats is someone from the outside getting control of your switch and rapidly cycling it on/off which could potentially cause electrical problems in your house.
That being said, these WeMo switches are the leaders in home automation smart switches. I have a few hooked into my phone and watch, as well as the IFTT service, which can have some limited use if you get creative with it. You can also pair them up with wall switches (I have not).