There is no integrated functionality to send SMS in webcamXP however it doesn’t mean that it’s not possible.
It requires a subscription with a SMS provider offering a HTTP Post gateway for sending SMS.
Something like www.clickatell.com
Then you have to setup webcamXP to perform the HTTP Post to this provider when a motion is detected and you’ll receive alerts by SMS.
At the time there were free providers working quite well but to my knowledge they have all stopped offering such service for free and this is why there is no integrated way anymore in webcamXP.