I've been perusing http://alphadoc.plantuml.com/doc/markdown/en/wire-diagram and it fond it very interesting.
Question is if it's still alive and kicking or not; in it's present state i don't think it's actually usable.
IMHO there are missing features (e.g.: arrows connecting two random components, not necessarily horizontal or vertical and auto-sizing) and a basic misunderstanding of needs and usage (sorry if this sounds rude, that's NOT intentional): This kind of diagrams are usually laid down in grids and they are much more visually pleasing if/when there's alignment of all components; using "turtle graphics" to layout is both clumsy and very difficult to modify if you need to ad/remove some component (thus defeating purpose to use a tool like PlantUML instead of "office like" tools).
I thus propose to use a syntax similar to one of the various layout-managers available (I am especially fond of http://www.miglayout.com/ which has an excellent "text based" syntax to layout nested "widgets").
Does this make sense?
If there's interest I could write up a complete proposal for this feature (and try to find some time to help development/testing).