VoIP Spear is a web service that monitors your VoIP QoS 24x7. It uses your Internet connection's packet loss, latency, and jitter characteristics to calculate an industry-standard MOS score between 1 (very poor quality) and 5 (very good quality). Log into your VoIP Spear account at any time and view your QoS history with easy-to-read charts. Furthermore, you can have VoIP Spear send you email alerts when your QoS drops too low.
VoIP Spear is free for personal use and very affordable for commercial use -- you can monitor your customers or equipment for as little as $1.00 per month.