Monitoring/Displaying Router Traffic to linked devices

Hi there

Not sure if this is the right place, so apologies if there's a better one, anyway here goes:

I've just recently got a WNR3500L and just put DD-WRT onto it, and its got lots of interedting and useful-looking features but it seems to be lacking the one of the things I wanted most of all - monitoring/displaying of traffic through the router to linked devices.

What I would really like is a visual way to see, separately and as an overall total, how much is donwloaded by each attached device (2 x wireless laptops and one cabled PC), over one hour intervals (and keep a record). If you know the Networx program (http://www.softperfect.com/products/networx/) then thats exactly what I want - but showing all the different linked devices.

So my basic quesiton is if there's any version of DD-WRT etc that has this as an inlcuded utility? Or if not, is there any existing freeware out there that would work with the WNR3500L and perform this function?? (had a bit of a google around but couldn't see anything obvious).

Many thanks in advance, MJK