This is interesting! I am surprised about your statement under http://synapcontrol.com/OurServices/tabid/92/Default.aspx
IP connections are not the optimum way to interact with most of the data gathering sensors and machinery being controlled in M2M missions today. SMS can perform most of the same functions over the same GSM network, cheaper, simpler and vastly more efficiently.
I thought SMS is old fashioned and expensive and an IP connection is the way to go today? I do not have to wait for the SMS. I can get (if I want) immediately response / feedback when the data package arrived on the server. I can trigger much different actions: Make this and that on the server, (with an additional gateway: send a SMS, make a call, ...) only with the interaction between GSM module and server without any SMS gateway.
What is the advantage of this additional layer!??
Note: Connecting to devices outside of the US or Canada may require some manual setup and could have a slightly different per transmit and receive price above the 0.10c USD.
This is also a downside for using SMS. All SMS services are highly connected with country related prices and also time delays (e.g. if I use the service in Europe but the SMS gateway is in the States).