Indeed, for those who aren’t familiar with the device you will need to solder on some headers and use a separate FTDI programmer to connect USB to serial input. Once that is done, writing some code to interact with the relay and indicators is fairly straightforward. However, for the more feature-rich products from Itead coding is going to be less straightforward. They do have a product that monitors energy usage (i.e. kWh) but creating custom firmware to make it a Web Thing is obviously going to be more involved. One interesting feature of the Sonoff is being able to pair it with a key-fob (an accessory from Itead). If you can get your firmware to talk via RF you then have a way of doing things like setting the WiFi SSID and password.
Once that’s done, share your code and we’ll all benefit.