thanks for your reply hugbug,
there are indeed multi wan routers, but those are or very expensive when they will use both connections to say double speed, other routers just use 1 of the two and have the other as fail safe. If i would be using the feature, it would be 1 adsl and 1 cable connection, so needing 2 bridged modems (provider based) and 1 router with 2 WAN connections.
Other options I would consider is to use a cabled network connection into my computer, and one using Wifi, so the connections actually are combined in the pc instead of at a router. This saves a lot of costs for the people using the option (people have often a cabled and Wifi connection in say laptop). You may even could combine your phone and internet subscription into one etc.
alt.binz works for the 2nd option listed above, and is used for this feature. It seems to assume 2 separate wan connections via the 2 different hardware components inside your pc, and uses both to grab stuff.
here is more info: http://www.altbinz.net/forum/closed-requests/multi-wan/