Specifically, I am looking to rate-limit an scp or sftp session (or other arbitrary network call) in the call itself.

For example, let's say I want to copy 100MB to one server, and 1GB to another. I'd like to be able to run both of these at the same time, but maintain a QoS for "normal" computer usage - somewhat similar to how you can rate-limit bittorrent.

Is there a way to do this without touching the networking hardware?

I'm envisioning something akin to:

magic-qos-tool 'scp file user@host:/path/to/file'

Or..

scp -rate 40kbps file user@host:/path/to/file