currently btdownloadcruses has information displayed with a pretty little hash line showing % done, how long.. how many peers, upload/download amount & ratio.
Could something be built into aria2?
1) is't aria2 is all about CLI and no UI? There are several UI's and GUI's for aria2, if you don't like them -- make your own.
2) doesn't "aria2c --summary-interval=0" give exactly what you are asking for?
Also, in aria2-1.2.0(now in beta) has built-in http server which provides download progress in html format.
could XMLrpc be used for this, for showing a pretty little progress meter? or does it already? :)