If you're looking for cheap and reliable devices, don't care about the whole Zigbee or Z-Wave debate and don't want to invest in XBee, then consider IKEA Trådfri outlets and Xiaomi Aqara devices. It's a near perfect paring. They're compatible repeaters with everything Zigbee it seems, including Xiaomi, and you get a simple ON/OFF switch in the deal.
Just buy a few. They're no where near as powerful as XBee (which is a good investment if you're also interested in seeing a map of your Zigbee network and monitoring performance).
