Merely proxies connections to a single server, and throttles the connection to a given speed in KB/s. This is useful for testing web sites and other network based applications for which latency and connection speed can affect the functioning or presentation of the program to the user.
I don't go to any lengths to ensure the speed is accurate, nor that asking for 500KB/s will get you 500KB/s, but I do guarantee if you ask to throttle it at X KB/s then you will not get faster than X KB/s.
Here is the --help output:
$ throttle --help
Throttle v1.0, (C) Chris Done 2010
throttle [OPTIONS]
Listens on port <listen> and proxies a throttled connection to <host> on
<port> at speed <speed>KB/s.
Common flags:
-l --listen=INT
-h --host=ITEM
-p --port=INT
-s --speed[=NUM] Speed in KB/s, e.g. 1.6.
-? --help Display help message
-V --version Print version information