I don't have a monitoring company at the moment, but many on the boards have used NextAlarm. I haven't really read anything bad about them. Again, I don't use them......
HW: AMD 3000+, 1GB, 250GB HDD, HS PCI Modem, Powerlinc USB, ISY-99 Pro/IR, NetCallerID, Waterbug, ~30 Insteon devices, and a few leftover X10s., ELK M1G
SW: XP Pro, HomeSeer v220.127.116.11, HSPhone,, CheckPOP v3, UltraStatus, DooNetwork, Powerlinc USB, BT Connector, HSTouch, UltraM1G,,, DooMotion, ActiveBackup, Powertrigger, ISY Plug-in v37