A small team from Mozilla has created FlyWheel which – as this post explains – is “an API for web pages to host local web servers for exposing content and services to nearby browsers”.
This is interesting because these browser APIs are useful for advertising and discovering local-area web servers, which opens up possibilities ranging from gaming to interactive applications. Right now it’s an early concept – the spec isn’t even complete – but should be interesting to see if this evolves out of the early stages.