Based on my experience, most GSM modems made by Siemens or Sony-Ericsson work well with ipMonitor.
Modems made by Multitech and Wavecom also work, however some clients have reported having a difficult time setting them up.
To my knowledge, there is no advantage or disadvantage between USB and Serial modems.
Hope this gets you what you need.
Chris Foley - SolarWinds - Support Specialist
Support: 866.530.8040 | Fax: 512.857.0125
network management simplified | solarwinds.com
Could you please let me know the GSM modem model for NPM SMS alert and is it possiable for (04) SIM?