Kannel still requires you to have a SMS provider or paired it with a modem as you mentioned. All it really does is give better control over your SMS in/outbond

Kannel still requires you to have a SMS provider or paired it with a modem as you mentioned. All it really does is give better control over your SMS in/outbond flow. I would recommend 41411 if you are going to server the US as well. I have used it with different applications, and still do. They have an API and you can get up and running within minutes. Best part, it is free.