Google Chrome's device mode has a subset of this functionality where you can make Chrome throttle the connection simulating different conditions (GPRS, DSL, offline, etc.).
Access device mode by clicking the smartphone icon on the top left of the Developer Tools (F12) right next to the Elements tab.
It's very useful. I discovered this the other day when testing some client side scripts. I was able to simulate a 3G mobile connection and determine which parts were causing the intolerable load times.
Access device mode by clicking the smartphone icon on the top left of the Developer Tools (F12) right next to the Elements tab.