I wanted one of my first posts to be helpful to anyone out there looking to do this. I made a script that helps you run a speed test on the client/customer's computer.
Requirement: The client/customer need to be able to download 1mb. If they are remoting in to you because they have a low internet connect/intermittent connection, then this may not be the best. The best suggestion would be to have them go to fast.com or to go to there ISP to verify internet outages or intermittency.
Many people use speed test websites to measure their connection speed. LMi.net has one as well. However, a more accurate test involves actually downloading a sizable file and measuring the speed averaged out over a few minutes. This is more reflective of a real-like scenario when you are actually downloading a large file, or streaming a movie.