Don't know about automatic bandwidth scaling but you could use:
wget --limit-rate=50k <mydownloadurl>
set 50k to whatever you can/want to spare. See man wget for more infos.
This is not what I want. I want that the download uses all not otherwise used bandwidth. It will use full bandwidth unless there are other tasks with higher priority. Given the fact that browsing the web is not very bandwidth intensive it would allow me to browse the web at full speed while only marginally slowing down the download. This is exactly what nice do for the CPU.
]]>wget --limit-rate=50k <mydownloadurl>
set 50k to whatever you can/want to spare. See man wget for more infos.
]]>