I have just bought a pair of these from fleabay. £13 each
Instructions very easy. No messing about with port forwarding etc. They just work.
I plugged a light into one to test. No problems, my android phone can turn it on/off from either the home wifi or when on a 4g network. I can even set up a schedule to automatically turn on/off.
What does disappoint me is I know it is ESP 8266, which I am starting to hack on my dev systems. It would be nice to be able to crack it open to inspect build quality and maybe hack the firmware on this so it no longer uses cloud service. But as it is a mains voltage device. I guess it is a good idea to not to make it an easy to open device.
If you have a need for remote networked switching. These things are great value for money