The Pushbullet - Send SMS Task lets you to send an SMS through your registered device to any phone number. A device could be a phone that you have linked to Pushbullet services.
Connection
Select an existing global Pushbullet Connection for storing connection credentials.
Phone number
The recipient phone number.
Body
The message of the SMS.
Pushbullet - Send SMS > Sending device(s) > Devices sub tab
Devices
Select a phone (among the devices) that will send the SMS.