Response Time Software

This may not qualify as completely on topic but I need to tap the vast knowledge of the Nanog group. I am in need of software that can give me response time statistics of our internet access points. We currently have multi-homed connections in various states and utilize proxy servers and socks servers for employee access to the Net. The issue is a need for a way to continously poll various Internet web sites via the proxy servers and socks servers to show average response times over time from various points on the backbone. Is anyone else doing this or have idea on what software may help accomplish this task. Please reply to me in private and I will post a summary message later on. Thanks, Derrick Bennett