Powerline kits and Wi-Fi range extenders are two of the most popular ways to fill in the gaps in your home network, and TRENDnet combined both products into one.
All you have to do is connect one of the included adapters to your router and plug it into the wall, then plug the other adapter into an AC outlet where your Wi-Fi coverage is lacking. That part of the kit includes two ethernet ports to connect wired devices, and it will also act as a tiny 802.11n router for everything else.
It probably won’t be as fast as a dedicated mesh networking system, and it obviously won’t be as reliable as running a new Cat5 line behind your drywall, but it’s cheap at $40, and only takes a few minutes to set up.