Not an expert on these things but they are said to be much better than wireless signals.
Lots of similar devices on page, these are cheapest for a pair.
High speed data transfer rate up to 200Mbps with Wire-Free feature
Plug-and-Play configuration with push button 'Pair' to connect two adapters without software
128-bit AES Link Encryption with key management to secure power-line communications
Build-in QoS feature to meet the requirement of online gaming & audio/video streaming
Easy Plug-N-Play operation, Use existing electrical wiring
HomePlug AV standard compliant, work with AC input of 100V~240V
Low power consumption